On the cheap you should stop at a store that sells black power and pick up some Goex 3f and some ball. Probably .490; rip up some old tee shirts for cleaning patches, make sure you have the proper sized jag. Get a pack of agate for flintlocks and some mattress ticking; Wal-mart might have both. While you are there pick up some Criso for patch lube. Good to go.
3f in the bore and pan, double edge agate in the hammer. Cut your own patches; a .50 cent piece is a good size for a .50 caliber. You will need a short starter to start the ball then ram it home with the ramrod. Lube your patches with Criso lard or olive oil. You can change it up as you learn but this will get you started as cheap as possible.
Things to watch for when your starting out. Loading a patched ball with no poweder in the barrel; called a dry ball. Not good. Failing to remove the ramrod; not good either. Swab between shots; spit or water is good to begin with.
Mossie has the right idea!! Keep you pan charge light don't over fill it and keep the touchhole clean.
Read alot on this forum and the traditional forum and you'll get lots of good ideas. Don't get frustrated and ask lots of questions. It can be tough but I think most will tell you it's a blast when it coems together!
Is see you are in Bangor, take a trip to dixons in Kempton, same exit off rt. 78 as dietrichs meats west of Allentown. They will hook you up right!
This. Go to Dixons. You can likely even buy a used weapon cheap, with all the supplies and advise you need. Practice, and get familiar with it. It's not a cartridge rifle. It's not point in the scope and dead deer.