Cheap units should be used
This depends, most importantly, on what kind of attack you want to pull, but many times instead of using a few active troops it is better to use many barbarians and archers. For example, dragons are awesome to use but your resources will be drowned, and it takes a lot of time to train them. If you want to get some dark elixir, so you are saving and looting, do not use it for the training of troops.
Every gem should be saved
Sometimes upgrading a building for fifteen gems seem like a good idea, but do not be tempted to do it. Every gem is very important. You should budget your gems and make sure that you always have an emergency amount. If you want to get more gems, all you need to do is complete achievements and remove bushes.
Your Town Hall should not be rushed
Even though you might be dreaming on awesome troops and weapons that you think await you ar the next town hall, do not rush the process. Your opponents get harder and harder to conquer with each Town Hall update so you should do everything as it comes.
Spells should be used properly
As a Clash of Clans player, you already know that spells are not cheap, and they do not brew in seconds. Besides that, only an amount of spells can be taken as an aid in battles. With that being said, you should always keep in mind that it can affect farming resources and that you should not use them at all times. Yes, it is tempting to drop a spell and win the battle, but if your expenses exceed your incomes, it will only become worse.