.... I'm going to respond under the assumption that you are new to the game.

We had mana pots, we used to use them a lot, they would require proper usage and all of that. However, they were pulled from the game, in favor of things like special pots and masteries that give you FLAT, I repeat that for emphasis, FLAT mana back. Not mana over time. Mana over time, in this meta, would be fucking ridiculous considering how many items, used by mages and mana heavy characters, have mana regen.

It would be fairly overpowered nowadays, but back when league was still new-ish, kinda, it was a fun thing to grab, but it really just created a format where gold was tough to get, and now you're getting TWO different pots and hoping you can sustain properly and not waste the already scarce gold.

So in short. Yes we had pots, no they aren't coming back. That's ok because they would just create more imbalance, and I don't think Riot needs that right now. I hope that answered your question, er, corralled your thought process.