I recommend that you download the hero designer from Midsreborn.com. That will let you choose any AT, powersets, powers, slots, and enhancements and see what the numbers for all your attributes will be. How much damage will a power do, how quick will it recharge, how much defense you will have, etc.
After you play around with it, you can post a build that you made and let build gurus have a look and suggest possible changes to make you even better!
Here's a thread with three similar builds made with MidsReborn. They look pretty good, but expensive. Still that gives you a good idea of how to slot and something to shoot for.