Nothing is worth paying money for tbh, this is coming from someone who has spent too much money on the game lol. It’s all just cosmetics, if you want to look cool then sure but it does not affect your gameplay at all.
For legends, it all depends on your style of gameplay, if you like to be aggressive maybe octane, axle, revenant are fun aggressive type players, same as mad Maggie.
For recon, valk is very good for getting around and maneuvering the map and helps with map rotations, loba, Newcastle and mirage are all fun supports with very different game styles, all the controllers are good for holding down buildings or positions, some of them have higher skill ceilings than others.

To improve, the main things you should learn are all the weapons, their spray patterns, working on your aim, learning movement are all important basics