If you haven't done any upgrades yet, I'd start with a pipe and a high flow air filter. You will need to upjet (and tune) your carb when you do that, which will be good practice for if you want more speed after that. It would also be a good idea to match the outside of the exhaust port to your new pipe, because it improves flow and it's (again) good practice for future upgrades. If you aren't happy with the speed with the pipe, then you could either get a bigger carb, or get a setup like this.
As for pipes, the Estoril and Proma GP are both pretty well recommended for stock cylinders. The Boss is cheap and will give you a performance boost (but it's not so good for low end) and the Bullet is pretty similar, although with perhaps slightly better low end than the Boss. If you let us know more specifically what you're looking to get (how fast, and how fast you want to get there) and how much you have to spend, that would help us give better recommendations.
I'm not sure if you've read the stuff on the wiki, but if you haven't, you should read the performance tuning page and the performance FAQ page.