There are .22 snap caps available if you like. Only ones I've seen are plastic so they don't last long & could get expensive if you do much of it. Plus, not as much fun as shooting at the range.
One reason I bought my GSG1911-22 is it had a rep of shooting the really cheap bulk ammo & mine did well with the Federal Bulk ammo, but you will get quite a few duds. Also, they have some kind of wax coating on them that will build up in the chamber & cause failures to go to battery. Just need to take extra care to clean the chamber.
A little better quality ammo, but not as expensive as the Mini Mags, is Blazer in the 500 round box & that is what I shoot the most now. One that I intend trying because it is supposed to be much cleaner is Winchester M22. But have only found it in 1000 round bulk pack at Wally World & I don't want to buy that much until I know it'll cycle in my wife's Bersa .22.
P.S. The earlier GSG .22s had a problem with the barrel bushing & they came out with an improved one to replace it. Might be a good idea to call ATI with your S/N to be sure if it has the upgraded bushing. If not, they'll send you one.