Because it is Clash of Clan’s 6th anniversary you can boost your collectors 1 day for 1 Gem each. So for 1 gem you can double the production, it’s a great deal. This event lasts till september 1st.

You can train troops in the barracks. With these troops you can attack other players or play the single player missions. It cost elixir to train troops. How much is depending on the troop. If you upgrade a barrack you cannot use it until it is finished. You can speed up the training using gems, the troops are instant ready. ...