What should i upgrade next defense-wise?

Hello everyone,i'd like to know your ideas on what i should upgrade/prioritize next defence-wise.
Big Bombs:Lvl 3,Reg Bombs:Lvl 5,Air Bombs:Lvl 3,Air Mines:Lvl 1,Skeletons:Lvl 3,Spring Traps:Lvl 1

Here's a screenshot of my base(any feedback is welcomed!):

http://prntscr.com/62lq0n

Thanks!:cool:

I don't know why you put spring traps in your list because you can't upgrade them.

But honestly, get those air traps upgraded. They're the lowest level trap on this list, so they need upgraded.

Seeking Air Mines. Invaluable in war, and cost the most.