Depends on what you are looking for, 300 is a wide open playing field. For factory ammo, I sighted in with the 120gr Remington's and use the 110gr Barnes for hunting. There are a ton of 147gr rounds out there loaded with military 308 bullets, and the subsonic game is huge, I haven't ventured into those since my suppressor is still in limbo.
Those 110gr Barnes are a great hunting round, took two deer last year with great results
If you do not reload, Sellier and Bellot manufactures some relatively inexpensive and fairly accurate ammo in .300 BO. I like the 147 gr FMJ loading, my Ruger American shot 100 yard 1.5" groups with it. They offer 124, 147, and 200 gr loads. The 200s are subsonic, haven't tried em yet.
If you search on google or ammoseek.com, you can price and locate whatever you wish. The S&B 147 gr is in short supply right now, I stocked up a few months back. It can be had for $10-14 a box when in stock.
I also have purchased several boxes of the Barnes 110 gr TAC rounds and Hornady 110 gr Z Max, for superior terminal performance.
Ditto Ozark Ordinance.......stay far away from them.