Pokemon GO Tips and Tricks -Pokemon Go: what items you get at every Pokemon Go level

Well leveling up in Pokemon Go pays off. Great Rewards and Unlockable items, at each Level.

Leveling in Pokemon Go gives you items that will help you better play the game. Some of the items will improve at higher levels.

For example, once you hit level 12 you'll be upgraded to a Greatball instead of a regular Pokeball. Though your bag has an item cap of 350, you can go over this item cap when receiving level rewards.

Leveling requires XP, which can be gained from a number of methods including: catching Pokemon, evolving Pokemon, visiting Pokestops and winning gym battles.

Level	Unlockable Rewards
2	Poké Ball x10
3	Poké Ball x15
4	Poké Ball x15
5	Poké Ball x20	Potion x10	Revive x10	Incense
6	Poké Ball x15	Potion x10	Revive x5	Egg Incubator
7	Poké Ball x15	Potion x10	Revive x5	Incense
8	Poké Ball x15	Potion x10	Revive x5	Razz Berry x10	Lure Module
9	Poké Ball x15	Potion x10	Revive x5	Razz Berry x3	Lucky Egg
10	Poké Ball x20	Super Potion x20	Revive x10	Razz Berry	Incense	Lucky Egg	Egg Incubator	Lure Module
11	Poké Ball x15	Super Potion x10	Revive x3	Razz Berry x3
12	Great Ball x20	Super Potion x10	Revive x3	Razz Berry x 3
13	Great Ball x10	Super Potion x10	Revive x3	Razz Berry x3
14	Great Ball x10	Super Potion x10	Revive x3	Razz Berry x3
15	Great Ball x15	Hyper Potion x20	Revive x10	Razz Berry x10	Incense	Lucky Egg	Egg Incubator	Lure Module
16	Great Ball x10	Hyper Potion x10	Revive x5	Razz Berry x5
17	Great Ball x10	Hyper Potion x10	Revive x5	Razz Berry x5
18	Great Ball x10	Hyper Potion x10	Revive x5	Razz Berry x5
19	Great Ball x15	Hyper Potion x10	Revive x5	Razz Berry x5
20	Ultra Ball x20	Hyper Potion x20	Revive x20	Razz Berry x20	Incense x2	Lucky Egg x2	Egg Incubator x2	Lure Module x2
21	Ultra Ball x10	Hyper Potion x10	Revive x10	Razz Berry x10
22	Ultra Ball x10	Hyper Potion x10	Revive x10	Razz Berry x10
23	Ultra Ball x10	Hyper Potion x10	Revive x10	Razz Berry x10
24	Ultra Ball x15	Hyper Potion x10	Revive x10	Razz Berry x10
25	Ultra Ball x25	Max Potion x20	Revive x15	Razz Berry x15	Incense	Lucky Egg	Egg Incubator	Lure Module
26	Ultra Ball x10	Max Potion x15	Revive x10	Razz Berry x15
27	Ultra Ball X10	Max Potion x15	Revive x10	Razz Berry x15
28	Ultra Ball x10	Max Potion x15	Revive x10	Razz Berry x15
29	Ultra Ball x15	Max Potion x15	Revive x10	Razz Berry x15
30	Ultra Ball x30	Max Potion x20	Max Revive x20	Razz Berry x30	Incense x3	Lucky Egg x3	Egg Incubator x3	Lure Module x3
31	Ultra Ball x10	Max Potion x15	Max Revive x10	Razz Berry x15
32	Ultra Ball x10	Max Potion x15	Max Revive x10	Razz Berry x15
33	Ultra Ball x10	Max Potion x15	Max Revive x10	Razz Berry x15
34	Ultra Ball x10	Max Potion x15	Max Revive x10	Razz Berry x15
35	Ultra Ball x30	Max Potion x20	Max Revive x20	Razz Berry x20	Incense x2	Lucky Eggg x1	Egg Incubator x1	Lure Module x1
36	Ultra Ball x20	Max Potion x20	Max Revive x10	Razz Berry x20
37	Ultra Ball x20	Max Potion x20	Max Revive x10	Razz Berry x20
38	Ultra Ball x20	Max Potion x20	Max Revive x10	Razz Berry x20
39	Ultra Ball x20	Max Potion x20	Max Revive x10	Razz Berry x20
40 (Max)	Ultra Ball x40	Max Potion x40	Max Revive x40	Razz Berry x40	Incense x4	Lucky Egg x4	Egg Incubator x4	Lure Module x4

Note that certain levels also unlock specific Items that will then become obtainable at PokéStops, including Razz Berries, higher tiers of Poké Balls, and Potions.

Pokémon Go encourages players to get out there and gain experience so that they can level up. But instead of leveling up their Pokémon, trainers themselves are the ones who reap the benefits of powering up. For every level you gain in Pokémon Go, you'll earn a set of items. Sometimes, you'll unlock new items to purchase or pick up at various PokéStops around the world.

Sources: 

Level Rewards and Unlockable Items

All of Pokémon Go's level up rewards and unlockables in one list (update) Polygon.