First should be walls. This game is won by defense.
Second should be rally spot. 100k waves are a wonderful thing.
Third should be Feasting Hall. You wont get 10 waves out at once without 10 heros.

A lvl10 Town Hall is pointless. All it gets you is 3 more resource fields, and one more valley. Plus it makes your castle bigger in map view, which makes you more of a target.