youi'll need a shotugn as well.
Word is the recent offerings from marlin kinda suck since they were bought ouit...by remington? a good used marlin that has had some breaking done is the way to go.
most folks shoot .38's for less recoil and for economy. I prefer to use 357 cases to avoid building up a 'crud ring' in my guns.
for the .44 cases i'd use a powder that fills the case up a bit,like Trail Boss,or maybe clays. a 185 or 200 grain bullet is all ya need,most folks go light.I use 200's as they seal the case btter with light loads.
I don't mean to scare u off,but if ur starting from scratch,guns and leather are gonna set ya back a minimum of 1500 bucks..not sure if it can be done for that these days.but it's a real fun past time shooting the ol' west guns.