My first played champ (and match) was with Pantheon. However, I had no idea what I was doing, even with my friends telling me what to build and do (just jump on them, stab them a bunch with E and then throw a spear at them and gtfo!) Also, at the time, my friends were probably around the high 20's or 30, I don't really know, and I was a level one in my first match, so we got destroyed.
Afterwards, I played some Dota on WC3, and found Sniper, so I asked my friends if there was a character in league like him, and they recommended me Cait, so I saved all my IP for her, bought her, and haven't looked back since.