Welcome to Selbina.

I can only say as long as you know recipes for armorer which you can find online you can level it anywhere as well as GLD, but the advantage of being in Ul'dah is the population and thus you'll hear /shouts that may pertain to you, such as: LS advertising, XP PTs, etc.

But @ lower levels I don't see why you couldn't stay in Gridania for the time being and get familiar with the city itself and area around it~