Sharkbyte, use about 70 grains of powder to start with - the volume equivalent of 70 grains of black powder, that is. This is a medium load, not too tough for target shooting and a little on the weak side for hunting. You can go up or down form there once you get more familiar with the gun.
A pound of powder contains 7000 grains and will last you about 100 shots. Substitutes like 777 are actually lighter than black powder, so you'll get more than 100 shots out of a pound when using the 70 grain volume equivalent. $20 a pound for 777 sounds about right.
Which powder is better? You will get a different answer from everyone you ask that. So let me tell you what I think of the powders and substitutes I have tried. Real black powder (I have used Goex so far) is often hard to get, fouls the barrel somewhat with corrosive residue and stinks like no other - it's the real thing. Easy to ignite, too, so any gun that is prone to misfire will benefit from using real BP. There are three types available here in the US as far as I know: Goex, Swiss and Kik. Search for "Swiss" and "Kik" on this forum to find out more about those.
Pyrodex is just as dirty as black powder in my experience and considerably harder to ignite. It comes as "P" (like 3F) and "RS" or "Select" (like 2F). The residue is also corrosive, so the rifle MUST be cleaned the same day after a shooting session.
777 is hotter than black or Pyrodex so the charge has to be reduced by about 15% (giving more shots per pound). The fouling is not corrosive itself, but it will attract moisture quickly, so cleaning the same day is also needed. It cleans up completely with just water which is kinda nice. The fouling can create a hard buildup, especially where the ball or bullet sits atop the powder - I had to swab the barrel with a damp patch after every second shot when I was using 777.
Then there is Black Mag 3 if you can find it. More expensive at $30 a pound but very clean and not corrosive at all. It also is a little hotter than BP,just like the 777, but ignites almost as easily as real BP. Overall the best substitute of the three by far, in my opinion.
There are others like Goex Pinnacle (rather new) and American Pioneer Powder which I have not tried myself yet.
As far as patches go, I would recommend that you buy some pre-cut and lubricated patches to begin with (around $6 for 100). .010 and .015 thickness patches are good for initial experimentation until you get a feel for how tight the bore on your gun really is and what ball/patch combination it likes. I like easy loading, and the .010 patch will ensure that. You can go for top accuracy with a tighter patch later when your rifle has been broken in. Places like Mid South Shooting Supplies sell these patches.
Cleaning patches (not the same as the ones you shoot with!) can be cut from old cotton T-shirts. I buy cleaning patches from WalMart that come in a bag of 200 for just under $2. I cut the big ones into smaller pieces of proper size. As has been mentioned, you will need a jag on your ramrod to get the patches back out again.
Before shooting I run a cleaning patch saturated with rubbing alcohol down the bore to get rid of the oil and then follow up with a dry patch or two. After cleaning I saturate a cleaning patch with RemOil and run that through the bore a few times to get the gun ready for storage.
I hope you'll have as much fun "smoking" as I do.
Steve