Enchanting will be the hardest and most time consuming but pretty important… Smithing without mods will also take a decent amount of time and be fairly annoying to do… Alchemy will be the easiest as long as you have the ingredients and know which potions to make. Alchemy is also the most important of the three, because if your really good at alchemy you can make iron weapons/armor that can kill several alduins in one hit and make a single piece of armor that will exceed the armor rating cap. Plus the added benefit of creating potions that will take you from 15 to 100 speech in a single transaction (it’s okay that npcs won’t have that kind of gold) plus alchemy is the fastest way to make money in the game at 100… I’d almost just worry about alchemy and then enchantment personally.

I’d go with enchanting. Gives you the ability to upgrade anything you find ans sell it for more.