@Selaphiel
Winchester and Remington are the top two when it comes to all of the most basic ammunition (9mm Luger, .45 ACP, .380, etc). Those two are also the top spots for hunting and sporting rifle ammo, I think. For “military grade” 5.56 and 7.62 rifle ammo (which simply means “loaded to the same stats as US Army FMJ training rounds”) the go-to is Federal/Lake City/American Eagle brand ammunition. Aguila (made in Mexico) is also fairly popular for cheap plinking pistol and rifle ammo, though I’m not really a fan of it myself. CCI is generally one of the best brands for .22lr ammo.
For AK-47/74 ammunition, you’re going to be dealing almost exclusively with imports if you want it at any reasonable price. Tula ammo steel-case is the most common stuff on store shelves, though the Wolf brand is popular but I haven’t seen that in stores that often. Both are made in Russia, and both also offer American rifle cartridges (.223, etc) in steel case as well. Academy has an in-house import brand called Monarch, which offers both steel and brass-cased rifle and pistol ammunition. The steel case ammo is made by Barnaul in Russia, and the brass case ammo is made by Prvi Partizan in Serbia. Century Arms has their “Red Army Standard” line of 7.62x39, 5.45x39, 7.62x25 Tokarev and 9x18 Makarov cartridges, and they have multiple sources, though the most common I’ve seen are Russia and Bosnia.