There's no one right way to play RuneScape (although many players will claim that there is, and call those who don't play their way a noob). Most people like to try a bit of everything as they level up, so that they have plenty of things that they can do when they fancy a change. However, there are other ways to approach the game. The main consideration is whether you train character level, combat level, or a mix of both.
When you create your character, you'll be asked to select an outfit. The outfits are themed around popular progression paths, for example, Chef or Ranger, but the look that you choose does not affect the way that your character will progress. You could dress like a farmer and then go out and train magic if you wanted to. All that you're selecting when you choose a character and a style is the way your character will look when you first log in to the game.