Wizard; better than you think, probably want to take it early. You'll end up with fourth level spell slots available to you, so you'll be able to spend gold to learn spells up to that level. Also rituals offer a ton of utility.

Realistically, you're building it as a martial right now, when in general I think it scales much better as a caster. Take wizard and warlock early, lean on Eldritch Blast (since it scales well with char level), pick up Fighter or Paladin relatively early for armour profs, then ignore martials to the very end (save maybe Rogue), because they really give you nothing but HP.

What's the achievement requirements?