Welcome to UZI Talk and congrats on the UZI. The most widely used ammo is the Winchester 100 round value pack in the white box. Avoid the Remington/UMC stuff in the yellow or green box. It's underpowered.
I used Bulk 100 round Winchester White Box from Walmart. I tried some cheapier brands from a gun show and found that my Vector would not shoot PMC Bronze. Gave up after trying to fire a few rounds of a Twenty round magazine.
I've purchased 1000 rds. on two seperate occasions, bulk MBI, 147gr. from Lucky Gunner for $250.00 delivered to the house, and it runs well semi and full, w & w/o suppressor, and brass the is fine for reloading.