From En Bloc Press:

The best way to avoid triggering these multiple handgun sales reports is simply to not buy two handguns at once, or to wait more than 5 consecutive business days between your purchases. You could also just buy one handgun at one FFL dealer and then another handgun at a separate FFL dealer.

There is no federal law which limits how many firearms an individual can buy at a time. As a legal gun owner, you’re not breaking the law by taking measures to avoid being reported to the ATF, provided of course that you aren’t actually involved in the unlawful trafficking of firearms.