for the best deals on ammo i would have to say it is silver state armory, same for brass.
most cost effective way would to buys some ammo then save the brass and reload
for mags I would say the PRI are the best and they are trying to get a group buy going, also visit the fine folks at Palmetto state supply
Welcome. Yeah Silver State Armory direct is a good way to go. Hornady ammo is popular also. Some say to be careful with the Remington 6.8 ammo, it's not always the most consistend compared with the other two. A few guys here are now shooting the new S&B 6.8 also.
PRI and Barrett mags have the best reviews for quality and reliability. Newer C-Products 6.8 mags are popular also, and much more reasonable in price at $15-17 each versus near $40 for the PRI and Barrett. I'd mix some C-Products with Barrett and PRI in the collection.