Garen is just fine. He is completely playable. He's not underpowered, or overpowered, he's just there. If you would like to purchase a new champion, choose one that you will use pre and post level 30. It is more valuable to save your IP for runes (debatable). I would prefer to say Garen, Xin Zhao is picked nearly every game I'm in, and is banned every game. He may have gotten nerf but I call shenanigans, he's just as strong.
Garen has a lot of neat abilities, like his ultimate (used to finish off people.) Aswell as judgment. I don't think his learning curve is really bad either. If you're looking for fighters (champions with survivability and able to deal moderate damage, like the two you listed) I would suggest either Jax, Udyr, or Olaf. They are very durable, but I think atleast one may take a while to master (I'm thinking udyr or olaf). Jax is a great start for learning to meele. Overall, it's upto you. If you would like to know any of the champions I prefer just say so.