>>27538831Dpeneds on your playstyle and how often you hit pokestops.
Do you like battling and taking over gyms? You'll need lots of room for potions and revives.
Do you like to catch everything you find? You'll need lots of balls and berries.
I bought 1 upgrade to my bags and I'm doing just fine. If you find your bags always full, filter out the items you don't need that day. Or buy more space. Easy peasy.
