Here are some tips to use.
1 always get the storm towers, ballistas and other dangerous assets before they have affect.
2 if you're defending, use the tools on the left by dragging them over the towers. They help drag out the battle and stack up your chances of winning.
3 level up your dragons to at least level 10 before using them on a base of a level twelve or above.
4 save up your time skips so you can use all of them for a truly high level tower.
5 be sure to put your sheep farms and lumber mills closest to the dragon den. That way you can defend them in a way that some of your opponent's easiest accesses to your lumber and food supply aren't so accessible.