Outer
The only criticism I would have is that there is a severe lack of anything in his life apart from this potion progression that we can see. I mean, some character interaction would benefit this ff a lot. It might be a bit boring but it will some personality to the MC. Also I like the fast pace so far and I understand why you are doing it the way you are doing it.
The potions and such for lower sequences can easily materialise from the system. But the higher sequences are occupied so I think an explanation for the system Obtainingthem may be required (e.g system is able to displace the item etc etc or it just guides MC to the item rather than hands it to him)