If you think about it a certain way, the game is as much about resource management as it is about anything else. The three "farmable" resources -- Gold, Elixir, and Dark Elixir -- are the obvious resources to consider, but this strategy guide encourages you to think of Trophies and Gems as resources as well. It also returns to develop further the point made in the Introduction about symmetry.
Players use Gold to purchase upgrades to their defenses and walls and to clear off rock obstacles, among some others. As with Elixir, upgrades cost more and more as the game goes on. For this reason, it is a good idea to make upgrading your Gold Mines a priority as often as you can, so that your rate of production more closely matches your increasing needs.
Of course, gold can be acquired by other means than farming. It is always an option to raid for gold, but it costs a lot of elixir and playing time to raise armies for that purpose (remember, symmetry), and since you lose your shield when you attack, much of that gold can be stolen in other players' raids on you. Still, as a rule, if you don't need a great store of elixir, but you do need more gold, raiding is a way to gain gold when your resource collectors aren't producing fast enough to suit your needs.
In some ways, unlike Gold, elixir can be more easily wasted. If you ever raise an expensive army, only to have it massacred in a wasteful and poorly conducted raid, you know what a poor investment looks like. With gold, at least, even if you upgrade the wrong buildings, they're at least being upgraded once the resource has been saved and spent, which is something no one can take away.
Also unlike gold, with elixir it is harder to gain more of it through raids, the reason being, obviously, that it costs elixir to build armies to then go raid for more elixir. And for that matter, it is difficult to acquire enough elixir in a raid to match the cost of the army you trained to fight it. On top of that, searching for a raid target with at least a sufficient amount of elixir costs gold as well. This is where it becomes important to achieve the best cost-effectiveness as you can out of your troops.
Dark Elixir, let's face it, is the one farmable resource that is hardest to come by. It does not even become a factor until Town Hall Level 7, and even then, it takes a lot of work to get a reasonable rate of production going. Early on, you have to rely more or raiding than you might like to.
The thing that distinguishes trophies from other resources in the game is that is the one resource that can be earned in battle only. No amount of money or gems can buy them, and no amount of scrimping, saving, and protecting can earn you more. For certain playing philosophies they are the most precious resource in the game because they are the main measure of long-term progress. Either way, of all the resource types, trophies are "The Great Leveler."
For "farmers," trophies hardly matter. In fact, they can be more of a liability than an asset because higher trophy levels attract stronger opponents. In fact there are certain styles of play that involve the deliberate loss of trophies as a means to achieving an end.
Acquired a store of Gems through hard-won Achievements? Got a check for $5 from your grandmother for your birthday? Gems are the one resource in the game that cannot be stolen or created. You can get more gems through achievements or by buying them or clearing off Obstacles, but achievements can be hard to come by, and not everyone wants to spend money or wait for the random gem box to give them a handful.
How to use Gems
Gems can be used for basically anything, but again, they are a precious resource, and certain uses are more cost-effective of them than others.
How not to use Gems
The best way to waste your Gems may very well be in the purchase of the fourth, or even the third, Builder's Hut. You're generally better off not using them to complete a building task, either. This depends on your style of play, though. If you are a particularly aggressive raider who is raking in Gold and Elixir hand over fist, you are probably taking in enough to justify the need for as many Builders as you can get your hands on. If you are the plodding, farming type (or maybe just not a very good raider), then your rate of production and acquisition is slower than your rate of building improvement. In that case, your gems might be better applied elsewhere.
Resources and "playing styles"
The following is a partial list of the "playing styles" described in the Introduction to these Strategy Guides. (Please read that section of the Introduction for background information on these playing styles in general.) It briefly describes the approach each type of player takes to each of resource:
The Trophy Hunter obviously views the other resources here as means to the end of earning Trophies.
The Grappler is in many ways the polar opposite of the Trophy Hunter where farmable resources are concerned. This playing style involves the careful protection of them, so that as little of them as possible is lost to raiders.
As has been noted before, other than trophies, there is no resource that the Jangler can't just buy. It only depends on how much he or she wants to spend (and how shrewdly he or she spends it).
The Vindicator is similar to the Trophy Hunter in this regard: resources are merely means to an end. The only difference is that, for the latter that end is trophies, and for the latter that end is revenge. The Vindicator may take some pleasure in robbing a target of as many resources as possible, but really that is icing on the cake. Depending on the approach taken to vengeance, the Vindicator may take particular pleasure out of stealing a particular one of those resources, but generally the Vindicator isn't particular about anything except revenge.