For 3 vs 4 cross http://www.bikeforums.net/bicycle-me...s-4-cross.html have build quite a few wheels, and have never seen need to any more than 3 cross.

For spokes,prefer double butted over single, lighter & stronger.

For budget, would look at building vs factory/prebuilt, if I hadn't started building wheels back in the 90's before factory wheels came out, wouldn't start now, as it's not cost effective unless you can get parts cheap / wait till their on sale.