Big question. What type of rifles? Hunting, Match, plinking?
Several good powders for .308
1. IMR4895
2 IMR4064
3. Winchester 748
4. Hodgdon H4895
5. IMR 4350 in bolt action with heavier hunting bullets
6 there are other good powders also. The ones that you can find locally at your sporting goods stores would be my pick to avoid shipping and haz-mat costs.
Primers the same. Some use Federal Match primers for match shooting. I use Remington 9 1/2's but Win, CCi, Federal, Remington large rifle primers will work.
You mentioned 8mm and I assume it's 8x57 mm Mauser? If so it uses most of the same powders as the .308. Have fun, read, read , read, and be careful.
If you decide to shoot Hornady bullets, buy their manual, same for Sierra etc. Lyman's 49th manual is a good data manual. ABC's of Reloading is often mentioned. The powder companies have a lot of data on-line for comparison.