I've not played Morrowind or Oblivion but I've played the other three in the series and a similar mechanic exists in Skyrim as well, although it's not possible to do it in the early game. If I remember correctly you make a potion that lets you craft better armour, then craft armour that lets you craft better potions.
It was much easier than that in the earlier games as you could make much more unbalanced spells (and enchantments too).
You could basically make a Fortify Alchemy 100 for 1 second spell, and because potion crafting paused the game, you'd cast it, open your inventory and voila, infinite potion crafting at max skill level.
It's worse than that: Make a fortify Intelligence poition. Drink that potion. Make another fortify intelligence potion - it will be a bit better than the previous one. Repeat that a couple of times and you can make potions that fortify your attributes by thousands of points and last for hours.
But potions need ingredients you say? Find a merchant that restocks the ingredients you want. Buy them. Close and re-open the inventory - the merchant should have immediately re-stocked. Neat. You could just repeatet that but that's too tedious. Instead, sell the incredients back to them. Close and re-open the window and buy all of the ingredient agiant. Close and re-open the window and the merchant will have re-stocked the total number they had before. Repeat for exponentially increasing stocks.
I never finished Oblivion, but as I recall, by far the most broken strategy was to just never rest, so you never leveled up. Enemies are scaled with your level, but you could get most of the benefits from improved skills, but not face stronger enemies that way.
Leveling in Oblivion was linked to the major-skills that you selected at character creation, so it was beneficial to pick the ones you didn't intend to use. That way, you could pump up the important ones without scaling up the enemies.
