If you are shooting patched round balls, Pyrodex RS, pyrodex P or Goex blackpowder ffg or fffg is the best. Stay away from triple 7.
Speer or hornady .530 round balls with either a .010 or .015 patch. As for something to carry your powder in, Buy a large powder horn. i find that flasks they sell these days do not hold enough powder for me. My horn holds a little over 1/2 a pound.