Welcome to the site, first.
Now do tell us if you are waiting on a complete rifle or a pile of parts.
This is in the shooting section, so I'm guessing it's a complete gun and the management and feeding of the rock-locked smokey pole is your focus.
Korect us when wee R rong.
Here's what i got to throw into the heap: You should FIRST, try real hard to find some longrifle folks LOCAL enough that you can get some first-timer mentoring. Tell us where you are, we may be able to flush some out.
Second, with regard to any rifle, you should try both sizes of balls and many sizes of patches. Getting the ball/patch combo good and snug without being impossible to load is a great way to start down the path to good accuracy and extensive shooting without wiping.
I would (as I am currently doing) develop a load for both FF and FFF. Reasoning: your gun won't like both the same and it surely won't like both at the same volume. There could be some point in time when you have access to only one powder, be ahead of that game. As the 54 can eat some powder, I'm developing target loads as well as hunting loads (total of 4).
Oh but wait, that's with water-based lube (saliva) only. An additional 2 loads will be developed for hunting, as an fat/oil based patch lube should be used for hunting when the gun may be loaded for extended periods of time. Be aware that the first cold/clean shot out of a bbl will generally land "outside the group" and that's the most important shot for hunting.
You can prime with any black powder, FF, FFF, or FFFF suit yourself, there are many opinions. Many folks don't care to keep up with two different powder containers and simply prime with whichever powder they use for the main charge.
Buy several flints, you may get 50 shots from one and 4 from the next. Always have a spare.
Expect your initial sighting/development sessions to land very low if the front sight has been left high. Don't worry about it, put a target above your target, aim at the top one land on the bottom one-develop loads. Then file/drift sights as needed.
Clean with water.
Displace the water with water displacing aerosol spray oil. Use heavier oil for long-term.
Good to go!