Bard or Thresh

Seeing how you are beginner player, I'd say Bard's unique playstyle might be too much for you. While Thresh is by no means easy, at least his objectives are clear, i.e. you know what you want to do all the time, unlike Bard who sometimes gets confusing, and requires even more cooperation from his team.

Thresh is weak this season but can work

Bard is difficult to play

Bard is a roaming support who needs good communication from his team to work... Then he also has his versatile ult that can be tricky to land correctly.

Thresh is a typical tanky support with an added ranged basic and the lantern save for allies. And the hook helps...

Thresh's kit makes him the of supports and is incredibly strong in the right hands. He can do just about everything and was even referred to as League's Swiss army knife. Thresh's biggest strength is his ability to opt in and out of fights. For example if you land a hook on an Amumu you'd have just gotten aced if you were a Blitzcrank. But you have the option of going in or not. The lantern lets you opt out of a fight and pull an ally away to safety (really great if an ally is caught out so you can avoid a 4v5). Thresh typically can initiate small to medium fights but not really 5v5's with his hook.

Bard is seen as somewhat of an alternative to Thresh as neither are masters of one specific area of play. His kit isn't quite as versatile as Thresh but he really has just as much potential. Usually Bard will require a bit more coordination with your team however. The ability to stun 2 enemies for 1.8 seconds from a decent distance with your cosmic binding is pretty nuts and if you can pull that off twice in a team fight you basically just won the game (q is up every 3.85 secs with 45% cdr). Bard is better at initiating team fights than Thresh with his ult and for getting his entire team in/out with his magical journey.