In Pokemon GO, players may notice that at the beggining they only have a select few different items to pick from, but what some might not know is that as you progress through the levels, you unlock the ability to find more and more items at PokeStops. Here is a list of some of the items you unlock in the first initial levels:
5 - Potions and Revives
8 - Razz Berries
10 - Super Potions
12 - Great Balls
While this list is not complete, hopefully it will help you through your journeys in becoming the next Ash Ketchum. Now go out there and Catch 'Em All!