Your not going to be picking your position, and your position is going to depend on what the team needs if your fast and can kick maybe you'l be in the back three, but if the team has a good back three then you might find yourself at scrum half or at center. and to be honest no one on the internet can give you a clear answer about what you should play without seeing you play. A lot depends on your tackling ability, ball handling skills, speed ect. But if its your fist time playing then your probably going to be moved around a lot.
If you're a good kicker and have good knowledge of the game, you might be a good flyhalf or fullback. These are the two positions that are traditionally kickers, but they are very different and for very different players with different body types and speeds.
Probably Scrum half, fly half or full back.
Maybe Scrum Half
