If I where you and looking to go cheap, i would just put in some high preformance spark plugs and wires, and jet the carbs. I also put a little bit of octane booster in my bike when ever i fill up, make it run nicer, and faster. Walmart sells this stuff called 0-60 octane booster that is pretty cheap
As for an exhaust I would just take off the goat belly and put flex pipes right back to the mufflers (thats what I did), some people put an H pipe, but i dont have the ability to weld so this was easy for me to do, and cheap. Just check your local state laws before you do this.
92 Vulcan 750
extended back rest
drag specialtys grips (goin to be changed)
front floor boards