I've had some friends in DotA that didn't like consumables because they didn't provide a permanent benefit. It's really silly tbh when you realize that they give a ton of gain. You should always (99%) after buying your 1 (2?) items at gamestart round out your purchase with potions with w.e money you have left.
Jungler: Generally means someone can go into the jungle/forest/neutral creeps from level 1 and make his own way there. If you enter the jungle later on in the game (when you have a considerable amount of levels), you're probably just going there because there's no good farm in lanes atm, and that's really just neutral creeping.
Carry: Someone who is item dependent and becomes very powerful lategame if he is properly farmed. See: Corki, Yi, Ashe, Jax, etc.
The third char without mana is Dr. Mundo. He uses his health instead, like Tryndamere.
Shaco got hit with the nerfstick this patch, so it might be a bit harder to play him. It highly depends on whether you build atk or ap shaco: both shine in different areas. He's very good at mindgames, so you might want to put him off until you're more familiar with the game as a whole. 1v1 he's not very strong.
Katarina...is weak
. She's been nerfed in so many patches in a row. She's fantastic for stomping low games if you're pro with her, but upper tier games rarely if ever see her.
I recommend AP kat, and rushing Rylai's. It's kind of necessary on her (Frozen mallet if you go physical).