Starting out, a lot of stuff will be locked until you're a certain level. Cash is necessary to buy new guns, clothes, and properties, while RP increases your overall level. The two biggest progression systems in GTA Online are cash and RP (reputation points).It takes about an hour, but the tutorial, in which Lamar takes you on a few missions, is a vital introduction to different aspects of GTA Online.
They subtly affect what level your skills start at, but it won't matter in the long run.
