Do you have a reloading manual ? If not, I would strongly recommend that you purchase one or a couple. Read it over carefully from A to Z. Especially the sections on safety & load development. The .264win mag is a excellent long range cartridge, depending on your applications & bullet selection. I myself run a 140gr Berger match grade hunting bullet, in my model 70. I have had very decent results with different powders that I have played with such as Re-22, IMR-7828,H-4831sc & Retumbo. My go to load for my .264 is the above bullet with a between min & max load of Retumbo powder as listed in the Berger manual.
As for the best powder, bullet, casing, primer etc... that my friend is for yourself & your rifle to decide.What works for me & my shooting irons my not work for you & your tool's.
Cheers