Title says it all. I recently hit 100 smithing and there's a crap-load of stuff I want to improve. Where can I find or buy the potions -besides- the guy's house in riverwood? My alchemy svcks so dont suggest to make some unless you know of an extremely fast way of training alchemy. Thanks very much

I think it's really just random loot, I don't come across them often, I horde them for their rarity. Blacksmithing can also be improved via enchanting

Alright then, another question for you. With 100 smithing, will I be able to improve something more with 20% better improvement gloves *and* the potion or will it be the same with just the gloves?

Try checking other blacksmiths's houses. Only places ive found any of those, though sometimes I find some in general store

I seem to remember reading on the Wiki that they do stack. Also, and forgive me if this is a dumb question, have you tried the apothecaries in just about every major city? You might have to go to every one, and only end up with a couple potions until they restock, but it's not like you need that many if you do all your smithing in one go.

everything stacks potions, gear, perks

AFAIK these can spawn in the alchemist's supply chest. (It's location below.)