It's difficult to buy a poor cartridge nowadays.
Check where you're likely to shoot to see if there are any restrictions on plastic wads, then pick a relatively cheap shell and buy loads of them.
If you've an auto, just choose the cheapest you can get. If something else, then it may be worth spending a bit more on something like Comp X, as the real cheap Velocity offerings can sometimes be fierce on the recoil.
Bottom line is never worry about the cartridge as it'll always be better than you are!