Fill out your signature line with your truck info and members on the site will be better able to help you...
That said, if you have an '06-'07 truck with a 48RE, it comes with upgraded clutches. You could get away with replacing your TC and valve body for mild power upgrades. I'm on the fence right now as to what I want to do. TC, VB, flexplate, input shaft, or just a TC and VB.
If you have an older trans, you'll want to upgrade the whole transmission. For example, a Sun Coast trans goes for $4700 or so around here not including any billet parts or TC. It does, however, have all the upgraded clutch packs and other goodies. If you go nuts with billet parts, it can cost $8k or more, but will hold 800+hp and take street/strip abuse.
I think I'm going to be cheap for now and do a VB and TC. About $2500 in parts and labor. My trans only has 9k miles, though.