...My experience shows that 1-2 grains under maximum usally gives the best accuracy. There are many good 308 powders out there. You just have to experiment on which powder/primer/case/bullet/and cartridge length combo that works best for your rifle.....
Most all commercial brass is great for reloading. They will last 5-8 reloadings. Do not hassle with military brass, too much time messing with primer pockets.
I hear that Winchester is the best, Federal, and Remington is junk, etc....But I have not had problems with either of these brands. PMC, PMP, Israeli, Speer, Hornady, all good brands. Norma, Lupua, great cases, big prices.... But get all the same brand and if possible, same lot....
Full length size them, with a small base sizer, if using RCBS or Lyman...., for first loading, then if using a bolt action, you can neck size, after first loading. Trim them to min length. Then, if you are anal enough, weigh them and sort. Also the bullets....
Next, get a long inert round, put marker on the bullet tip, and put in the chamber. Reduce the OAL till there is no rifling marks, then reduce .03 less for bullet variance...
Primers, Winchester is the hottest, CCI, the coolest, try them all with powder combo's. Powders, RL-15, Vargant, AA2520, AA4064, AA4895, Winchester 748,760 IMR 4895, 4064, 3031, VihtaVuori 540, 150...try these to start. Start at Starting loads, go up .5 grains, to max load. Take the marked rounds to the range, and start seeing what groups you are getting with what loads are the best. Try different bullet grips, light to heavy....
After all that, you might get a round that is better than factory ammo...