I have the one KAC mag that came with mine, and about 12 PMAG LR's. No issues with either so far, and the PMAGs are 20 bucks.
Ive shot some match ammo, and some Hornady SuperPerformance. Other than that Ive shot Wolf, PMC, Silver Bear, and old 74 OFV Indian surplus. Had zero failures so far in 440 rounds.
Id order some type of decent FMJ online. I just ordered a bunch of PMC for $12.99/20. Hopefully by the end of the year brass case new FMJ rounds are under $10/20.