What all do you have done so far? I would start with the basics and go from there if you aren't looking to go crazy. Intake, exhaust, headers, cam, pushrods, springs, shift kit and of course a good tune! Depending on what you want your long term goals to be, then you could go FI, spray or heads. You already have a great building block to start with that can make some big numbers. Just depends on how big you want to get.