I've only ever shot percussion, not flint, but I'm pretty sure percussion is going to be a lot easier to get the hang of than flint. It pretty much goes ban every time!
For a pistol you will want FFF powder, or it's equivalent if you use one of the BP substitutes.
You'll need a cleaning rod and jag for whatever bore size you go with. A ball puller is handy if for some reason you can't get the gun to shoot. Likewise a worm for pulling out patches that get stuck in the barrel.
Use pure lead for your ammo.