I generally avoid, the "what do I need" questions. The list is always longer than it needs to be. here are always items that you buy that may never be used again.
There is what you positively can't shoot the gun without, and the stuff that comes in handy and the stuff that is nice to have.
Positively need, a) powder. You bought a pellet but loose black is so much easier to adjust shots with. also more sure fire. Extra flint and leather strip. Don;t buy cut flints, square look like shiny sawn agate from a rock collector store. My preference is an English flint, uniform translucent gray. Hold it up to the light and check for cracks. It should look sort of square from the top and from the side, like a flattened triangle. No muddy looking swirls. You can use 3fg in both the barrel and the pan, but 4fg is better in the pan. a touch hole pick, (a large paper clip should do. balls and patches. Don't get excited about whther the patches are .010 or .30 thick. In fact, try some old rag sheets, you may have as shop rags. I have found that patch material and thickness is less critical as long as the bore is sealed. and a powder measure. and a ball starter.
probably good to have, a pliers, a screw driver, a ball puller attachment, a patch worm, a pan primer , a horn or flask. Those round brass cylinder ones are ok. A small funnel. a range rod (a stout ram road longer than the barrel for ease of loading at the range and cleaning afterward.
There are some things that will do in a pinch. Like an empty cartridge case for a powder measure. A crab mallet for a ball starter.
One of the side things most "buck skinners" find so enjoyable is making their own gear. an antler tip powder measure, making their own horn, ball starter, molding their own balls, their own possible bag, etc. Most can be made with no special tools.
The excitement of wanting to get to the range, often has folks buying far more than they need in accessories. I;d be anxious to get to business too.
