The Tinkerer can be found at spawn or if you are rich enough you may have his moveable head in your cell or if you are Rank 2+ you may have access to the command /tinkerer. Either way, he will be somewhere for you to access.
If you have some extra gear which you don't want or tools, he will gladly to take them off your hands for cosmic energy. You can then use this cosmic energy to enchant different gear or tools which you are using and want to level up.
You can also trade in your enchant orbs which you no longer want and he will give you mystery dust. Mystery dust is a form of dust you get when you tinker an orb. The mystery dust will be the same rarity as the orb you have just tinkered. You then have a chance to fail or get the dust from it, which can vary in percentages throughout the tier it is in.