How much XP do I need and what items do you get for each trainer level reached? If it's not random does anyone know what items you get at each level.
The rewards are the same for everyone and can be different per level. For example up to level 4 you get 15 Poke balls and after that you get multiple items. There is a handy table with the different items and XP required for each level.
Remember that leveling up isn't just about the items you get. The key benefit is that you unlock items (also on the table I mentioned above) and can capture higher CP Pokemon.
Everyone get the same rewards.
Here you have the first 9 levels rewards list for everyone:
Level Unlockable Rewards 2 Poke Ball x10 3 Poke Ball x15 4 Poke Ball x15 5 Poke Ball x20 Potion x10 Revive x10 Incense 6 Poke Ball x15 Potion x10 Revive x5 Egg Incubator 7 Poke Ball x15 Potion x10 Revive x5 Incense 8 Poke Ball x15 Potion x10 Revive x5 Razz Berry x10 Lure Module 9 Poke Ball x15 Potion x10 Revive x5 Razz Berry x3 Lucky Egg
You can see the complete list here: Level Rewards and Unlockable Items