Get all the parts you need, then do all the work. Otherwise, you touch things too many times. Productivity will save you headaches. Shop around. You could find deals on the things you are looking for and save some money if you were to piece it together over a certain amount of time.
And after the work is done, get it tuned. Shop around for a decent shop or tuner, and make sure that is the number one investment.
My .02.