Part of the trick is to find what that rifle really likes.
Standard Velocity ammo will generally show better results.
Buying 5 or 10 boxes of ammo and dedicating a day at the range to test all of them in a consistent manner will show preferences. Shoot at a distant that will show differences . . . 50 yards or meters although I will often test at 100.
Cost of ammunition may be a limiting factor but value is where you start and finish. CCI SV may be found at $5.00 per box and Match will double that to as much as $20 per 50.
Start with a clean barrel and shoot one brand for 50 rounds at five targets on the same page in the same order every time. The first ten from a clean barrel will tell you as much as the last ten. The point of impact for the very first shot is also of interest. After your first target, retrieve it, make notes and post your second target.
Don't rush and be consistent.
CCI SV may be as good as it gets. CCI SV comes in a box (50) and Plastic trays (100). They are manufactured in different factories and one may prove better that the other.
Talk to ten shooters and all will have a different preference.
If you really want to shoot high velocity the same testing. Some rifles will show a preference to lead bullets (Blazer), others copper coated (CCI MiniMags) and now CCI has added a polymer coating calling them "Clean". There is a difference when shooting CCI MiniMags so testing both round nose and hollow points is worthwhile. One test at 100 yards produced 2" groups with RN and 6"+ with HP.
Testing under consistent circumstances is important. Wind, rain, cold and humidity may prove a change and it is time to quit for the day.
Since the original post did not specify scope, sand bags, bipod or any other set up it still comes down to consistency. There is a word for those that try the same thing over and over expecting different results.
Since he has a CZ 452 that shoots lights out, generally shooters go up in quality keeping in mind some are trying to keep under $500 for Precision Rimfire. We don't know.