Actually, having a bad connection isn't all that bad if you want to enter a tournament, as in most tournaments, collisions aren't enabled - simply because not everyone has a great connection and some people's lag makes it quite hard to have nice games. So you could enter a tournament straight away.
As for which tournament, there are many nice ones. The biggest tournaments right now are T-100, 18-S, Legends and MasterF1. T100 might be the right place for a beginner, as they're doing pre-season races now, and they use traction 100, which perhaps is the easiest way to drive a car. But if you would like to go faster and try driving with no traction control, you could also try 18-S. Driving in T0 (no traction control) might be a bit more difficult than T100, but IMHO, it's much funnier and more rewarding, so you could try driving in 18-S as well.
Legends and MasterF1 are also great tournaments. The problem is that they use both T100 and T0, and that's not something that I would advise for a beginner. I think that it's best to learn first how to drive in either T100 or T0, because if you try to learn both at the same time, you could end mixing up both styles and that's no good.
Whatever you decide, I hope to see you around soon!