Fiora or Trundle.

Trundle. He's a lot less stressful and isn't a win lane or lose champ.

Fiora is a slayer, a lower HP, high damage, bane of all tanks. She has a high skill ceiling but a relatively low skill floor. If you master her you can climb like crazy. Her downsides are that if you can't snowball you will probably lose. Trundle is a juggernaut, high Hp, tank, good damage, and an amazing duelist. Nonexistent skill floor and a pretty low skill ceiling. He's pretty good all game and his only real downside is being able to be kited.

Fiora is more fun to play, but Trundle is easier to be helpful even if you're not doing well. Trundle can also play more roles like jungle and support if you don't want to be stuck top lane

is a great duelist, sustain champ, split pusher, tank and anti tank

he can be top, jungle and support