A bunch of my friends are picking up LoL recently and I'll tell you what I've told all of them: try Garen. He's one of the easiest champs to play since he has no skillshots and doesn't have to manage a second resource. He's also only 450 IP which doesn't set you back much if you end up not liking him. If you end up enjoying Garen, you can learn the mechanics of the game while playing him and move onto other champs later.
Olaf and Jarvan IV are solid in both roles. Garen is an easy character to learn, and plays top well. He was my first champ. The only problem with him is he is very predictable. Looking back at the thread Jax is definitely a good choice too.