<edited 27/5/16> Preface
Reader beware!
This post was created more than a year and a half ago. The game has changed significantly since then through various updates. I have since retired, having enjoyed my time but burned out by the epically unexciting chore that upgrading walls at higher levels became. This post does, hopefully, still contain information that would be of value to newer players. But I cannot guarantee the details. Please keep that in mind should you choose to continue reading – and if you do I hope you enjoy.
With my Clash of Clans war post being the most often viewed on the blog, I decided to follow it up with a general levelling guide.
Levelling
Winning battles in Clash of Clans will cause you to improve Leagues. Apart from the one off gem award for achieving a new major League level (Silver, Gold, Crystal, etc), the only benefit of being in a higher ranked League is that when you win a battle, the bonus you receive is greater.
However, there are a couple of trade offs. Firstly, the cost of entering combat, or switching targets when attacking, is greater at higher levels. Also, you will generally find more higher level players in the higher ranked leagues. This means people attacking you with more powerful armies, while at the same time having more powerful base defences.
So, while leveling in COC, the best progression happens as a result of finding the optimum league level in terms of reward for effort. There is no formula for this because the populations of leagues are so dynamic. But you want a league where you can find opponents with enough resources to be worth raiding, but not so tough that your troops wont be able to penetrate their defences.
Most players will find that they naturally accrue trophies faster than losing them. So to stay in your optimum league range it will sometimes be necessary to dump trophies. This usually entails a series of attacks with a single troop that quickly dies. I used to use a single archer and seek a mine or elixir drill on the outskirts of my opponents’ base, out of range of defensive towers. Thus, I often would make a (small) profit in terms of elixir cost while lowering myself to hide in less dangerous leagues.
This trophy dumping technique is also useful when saving up large amounts of resources for a specifically targeted build. Hiding in a lower level where opponents capable of stealing large amounts of your resources until your mines and drills generate the last amounts needed.
Base
While levelling, it is a common strategy to keep your Town Hall outside of your walls and defensive tower range. When destroyed, the Town Hall surrenders only a small amount of resources, and causes you to have a shield to protect your base for 12 hours. Meaning that nobody else can attack you unless you break the cover of your shield in your own offensive attack. Once you are high enough in the game, you come to expect that every time you attack, you will get attacked back. But the preference is that you only get attacked once for each offensive raid you send.
Protect your stores. Keep them under the protection of your defensive towers including air defence. Do not cluster them all together in a bunch. I love bases that do that. My entire strategy becomes finding a way to get in to that cluster.
Don’t rush to end levels. Many people rush to Town Hall 7 to get their Dark Elixir and Barbarian King. But at Town Hall 7 & 8 players should really focus on catching up their upgrades to their Town Hall level. Most advanced players recommend maxing out all upgrades before advancing beyond Town Hall 8.
There is a rule of diminishing returns for Town Hall levels. The exact formula has changed but in essence, when a player attacks someone with a lower Town Hall level than they do, they see less of their resources available to be stolen. Rushing to Town Hall 10 can leave a player in the unenviable position of not being powerful enough to take on other Town Hall 10 players, while getting reduced raiding from players of lower Town Halls. As a rule of thumb, a player should not consider upgrading their Town Hall until;
(1) They can successfully win raids against most opponents of a similar town hall level, and perhaps even some with higher level Town Halls.
(2) Their base’s defences can hold their own against opponents with a similar Town Hall level.
Do not ignore your walls. I broke out in laughter the other day when I came across a base with level 10 Town Hall, and a mixture of level 4 and 5 walls (level 5 are the yellow ones). Easy pickings.
Do not ignore spells. Some players avoid spells as a cost saving exercise while levelling. But they can make enormous differences in success rates and are often mandatory in a warring clan.
Clan
As soon as possible, build your clan castle and join a clan. The best clans are sociable and friendly, and will not leave you hanging for reinforcement troops unless you are very picky in what you receive. Clans expect you to donate reinforcements in return and many popular clans expect players to target a donations given/received ratio around 1:1. They also expect you to participate in Clan Wars.
Being an Aussie player, the best clan I found was one that is locally based and consists almost entirely of fellow Australians. This means that players tend to have similar peak play times, which is useful in the other aspects.
Raiding
The ideal with raiding is maximising your Return On Investment. Ideally, you want every raid to turn a profit. In some circumstances, you may be prepared to make a loss in elixir to achieve a target in gold or dark elixir, but as a general rule for raiding, you want to come home with more than you spent on forming your raiding party.
Know how much it costs to build your army. A raiding force full of Dark Elixir troops may look incredibly sexy, but it means that unless you are finding opponents with enough Dark Elixir to cover their cost, you are operating at a loss.
This link will help you work out the cost of your army.
Troops
Barbarian. At higher levels, the only Barbarians you will see are those spawned by the Barbarian King. As a rule, Barbarians should not be given as reinforcements unless specifically asked for. They are a cheap mass produced troop who are best used as bomb-sweepers for your more valuable troops. They will attack the closest structure or enemy.
Archers. The default reinforcement troop due to their ranged attacks, cheapness and ease to mass produce. Not the most powerful offensively, but a strong ratio of quick to powerful for farmers trying to maximise their Return On Investment. They will attack the closest structure or enemy.
Goblins. These should never be given as reinforcements unless specifically requested. They are cheap, fast, and will ignore everything else to get to the closest resource storage or mine/drill. They just want the loot and will only attack other structures once all the structures containing resources are gone. Best used when dropped behind other troops that draw defensive tower fire to mop up the outstanding resources.
Giants. Slow lumbering meat shields. Generally considered an offensive troop only and should not be given for defensive troop requests unless specifically requested. Some players do like them anyway, but most in my experience don’t because of their slow movement. Offensively, good front line troops to draw defensive tower fire. If combined with a healer, can be incredibly powerful. Will target the nearest defensive tower first, ignoring other structures.
Wall Breakers. These fast moving suicide bombers are there to (not surprisingly) break walls to allow other troops through. They are weak and best deployed behind Giants or other troops so that they aren’t killed before reaching the walls and exploding. These should never be given as reinforcements. If specifically asked for, maybe, but I have never ever seen anyone ask for a wall breaker. In most clans, it is a cardinal sin and grounds for ejection from the clan to give a wall breaker as a reinforcement.
Balloons. Flying offensive troops that will target defensive towers first. If levelled high enough, I have seen plenty of successful all balloon attacks. Usually okay to offer as reinforcement troops.
Wizard. The core damage machine in terms of cost per unit to damage output. Keep these guys levelled up and they can tear apart bases. Having a cluster of them under the effects of a rage spell can cause maniacal giggling. Also these are often the core reinforcement troop used in clan wars. They can be a little squishy, so best deployed behind Giants or other tank-like troops.
Healer. Flying unit that will restore health to troops clustered together. Not much help when combined with fast moving troops like Hog Riders because they cannot keep up. Also the healing is usually not powerful enough to keep weak troops like Archers alive while under fire. But linked to Giants, Golems and Witches, the healer can keep these troops alive far far longer than they otherwise would have. Unpopular as a reinforcement troop, but not necessarily a no-no. It is good form to ask if okay before giving one. Defensively, they will heal your base as it is being attacked, but that really just slows the rate of destruction in the hope that it will give the defensive towers time to pick the raiders off.
Dragon. Sexy flying damage machine. A little slow moving, but not hindered by walls at all. Plenty of raids and even war assaults are all or mostly dragon attacks. Unfortunately, they are pretty expensive to create and can be give a disappointing Return on Investment against bases with strong air defences. Safe to give as a reinforcement troop in most any circumstance.
PEKKA. The slow tanky damage machine can be pretty powerful. But his vulnerability to lightning towers that could pop up most anywhere add a degree of risk. Combined with the relative expensiveness and long build times, not a frequently seen unit.
Minion. The early flying troop. Basically an archer with wings. Does okay damage, but a bit squishy and can quickly be wiped out by decent air defence. At the same time, relatively cheap to produce. Not a popular choice for reinforcement troop donations, but at the same time, not often rejected.
Hog Rider. Fast moving. Decent damage. Will target defensive towers jumping over walls to reach them. As a trade off, they are a little squishy and most successful hog raids involve well placed healing spells to keep them alive. Very popular in higher level raids, though less popular at the Championship level leagues where many bases are specifically anti-hog designs. Desirable as an offensive reinforcement troop and acceptable as a defensive one due to their movement speed.
Valkyrie. The forgotten unit. Capable of quality offensive damage and reasonably tough. But she is almost the middle child of dark elixir units. I hardly ever see her used, though she can be to good effect. Okay to use as a reinforcement troop.
Golem. The mega tank. Slow moving with lots of health. Designed to take punishment while the other units deal it out. Spawns mini Golemites on death that while not very powerful in their own right, will help draw fire away from your other troops as well. Will target defensive towers first. Should only be donated as a reinforcement troop if requested or okayed by the requestor.
Witch. She has a ranged attack and minions, being small skeletons that aren’t especially powerful. But the Witch is surprisingly resilient. Her skeletons are good at drawing fire from defensive towers and I have often had raids where the witch is the last unit standing. Popular at the highest end combat. Plus she is just fun to watch. Generally okay as a reinforcement troop and sometimes popular in war defence requests.
Heroes. I have seen some players ignore levelling their Barbarian King and Archer Queen because the levels have such incrementally small improvements. But the difference between a level 2 and a level 15 hero is clearly visible, and at top levels, these units can make all the difference. They each gain an activated ability at level 5. For the King, it is a haste aura, self regen, and spawns some barbarians. For the Queen, it is a stealth effect making her free from being targeted by defensive towers, some regen and spawns some archers. The potency of these abilities improves every 5 levels for the heroes. Invest the time in these guys and you will not regret it.
Save your gems. Some people have cash to burn in buying gems. Most do not. Gems are earned through achievements or by harvesting trees and plants that spawn around your base. Many bases have pristine areas completely free of such spawns. Those that don’t either tend to suggest that the player has all of his builders too busy, or that they are inactive.
Spotting inactive players can be very helpful to farmers. First, it suggests that the raidable gold and elixirs will be located in the mines and drills instead of in the storage buildings. It also suggests that traps, clan castles, and towers with ammo will be empty. Look for a build up of tombstones, a blank league badge well in to a new season, sleeping builders because nothing is getting upgraded. Also, the gold mine has a little bin on its right most corner that visibly fills up as its capacity is reached. All mines full suggest that the base owner has not been around for a while. You can also spot X-Bows that have no ammo. All are indicators of inactivity, but not a guarantee. I have personally left tombstones around to lure opponents in to thinking my traps and ammo defences are not loaded.
Also, there is a PVE mission element raiding goblin camps. They don’t seem to reward much but the last couple of levels increase rewards significantly. The last level alone is worth about 1 million of each resource. Also completing the chain awards an achievement with gems.