Buy any weapon
When you are buying bikes press: Up, Down, Left, Right, L2, R2.
More speed
Press Up, Down, Up, Circle, Triangle for more speed.
Playing Tips
Road Rash 3D is very different from previous versions of Road Rash, especially in its realistic riding. I recommend that for the first time you play a Big Game, use the Techgeist entry-level bike (DeMoto 500), because it has the best handling, and is definitely the easiest to use. Avoid the DeSades bikes, because they're neither incredibly fast nor very good at handling. The Dewley bikes, are the fastest on the straights but slowest in the corners. And the Racer bikes are the fastest, and the choice of advanced players bacause of their speed and razor sharp responses, which can be a hindrance to less experienced Rashers.
Before you permanently blow all your cash on a new bike, be sure to save the game before you do so. Then, if you decide that the bike is just not right for you (or it just sucks, period) you can go back and get a different one. Before you go on to level 2, BUY A NEW BIKE. Level 2 is hard. Not TOO hard, but it is a difficult transition from level 1. If you don't have a new (2nd stage) bike, you're screwed. I have a DMG 747 and the races are still hard. I'm not sure if I want to go to level 3.
Anyway, bikes aside, you NEED TO SLOW DOWN INTO THE CORNERS. If you don't, you'll find yourself sliding across the asphalt, onto the shoulder, and possibly up a mountain side. Another important thing is to lean more often than you expect. On a gradual turn, mashing the D-pad will send you sliding to hit a car or flying off the bike. Speaking of cars, there's a lot more trafficthan other versions, especially in the towns, with the multi-lane roads.
Oh yes, and another cool point of Road Rash 3D is that all of the vehicles are real, and I must've seen maybe 20 different models, from a Dodge Ram to a Honda Civic CRX. That about wraps it up. All in all, time trials are a great way to learn the tracks, thrash races are a good way to learn to fight while racing, and the Big Game is just pure fun.