The Master is necessary for crafting higher-end items - a few Tier 5, but mostly Tier 6+. You don't need to hire him until you get to that point!

Note that he doesn't come with any of his own blueprints. He's a secondary crafter for the items from other blueprint lines! If you're looking to level him up, the following items only require him to be level 1:

Katana

Battleaxe

Raptoria

Paladin Plate

Savage Garb

Knight Heaume

Pirate Hat

Knight Gauntlets

Savage Claws

Savage Stride

Knight Signet