That's an extremely open-ended question. "Speed costs money, how fast do you wanna go?"
Do you have an auto or 5-speed? Is this a daily driver that will need to pass emissions inspections? Are you interested in supercharging, turbo or nitrous, or do you want to stick with just bolt-ons? What level of power do you have in mind?
Switching engines can be very expensive if you are thinking of going from a V6 to a V8. It's not just the engine that needs to be swapped. There's the rear end, exhaust, suspension, computer, motor mounts, wiring, instrument cluster, transmission, and brakes too. Believe me, I have researched this a lot for my own car.
Some good basic power parts to start out with are dual exhaust, rear gears, cold air intake, and pulleys. You won't set the world on fire, but it's a start.