Learn them all. You don't have to powerlevel them, or put skill points into them until you want to use them, but they're all potentially useful.

Start trait research in blacksmithing/jewelllery/woodworking/clothier as soon as possible; without this you won't be able to craft any useful gear... completing this takes a very long time.

Levelling will come naturally as you deconstruct items, especially with the Intricate trait. (Note that deconstructing items you crafted yourself gives much smaller gains.)

Enchanting: deconstruct lots of glyphs (high-level ones are better) to level.

Alchemy/Provisioning: Brew potions/ cook foods+drinks to level.