Yea I looked up pictures and old retail information on them and to be honest I don't think I would spend a penny over $500 for a Thompson center rifle. The world's fair version looks just like any other. I saw a few on gunbroker selling at $800 and $900 and I couldn't justify spending that on a gun that doesn't seem appealing. Yea I definitely will be up on the watchtower looking for better deals.
OK. First of all, I want to congratulate you for all the enthusiasm you have to shoot BP. It is great to hear. As you know, there is so much information and opinions out there, that it is really hard to sort a lot of it out. First of all you really should buy a lot of FFG black powder. Once you start shooting, you will be surprised how quickly it can be used up; not to mention the shortage of powder these days. If you ever get "out" of traditional muzzleloading, you would have no trouble finding someone to buy it from you.
POWDERS
Specific to shooting Patched Round Ball, in my opinion, the best powder (and most expensive) is Swiss. Second would be Schuetzen. Third would be GOEX. Fourth would be Old Eynsford. Now, these are all really good powders with the last 3 being more affordable. The real issues are:
(1). Which powder works the best in YOUR gun?
(2). What amount of powder works best?
( 3). How thick of a patch to use?
(4). How accurate is your gun? Now if you have unlimited funds and time, you could buy all the powders and shoot all kinds of combinations till you find the right load. For me in my .45 TC Seneca, I use70 grains of GOEX FFG, a .440 round ball and a #18 pre-cut patch which I sparingly lubricate with Mink Oil.
LUBES
Seems like there are a million kinds of lubrication recipes out there. Everyone has their own favorite. Some use Bore Butter, Crisco, Olive Oil, Bees Wax, Windex, Moose Milk, Bear Tallow, Spit, you name it and the combinations go on and on. Personally, I use Mink Oil. It comes in a can, it's easy to use, it has no petroleum in it, it is all natural, it doesn't get rancid, and it doesn't harden in cold weather.
GUNS
Starting out, there was no question for me that I wanted to use a straightforward rifle and not some variation that might be somewhat narrow in scope. By this I mean the first gun might have been say, a .50 Caliber Hawken. From there, people get into other variations such as Fowlers/Smoothbores, Under-Hammers, in different calibers, etc. Some only hunt Whitetails, others small game, squirrels all which require different calibers. One wouldn't hunt ducks with a rifle, etc. I don't have the luxury to have a number of MLs to use, so I decided given where I hunt and what I hunt (Whitetails), what would be the most all-around rifle for me? Therefore, I chose a .45 caliber. A .45 can pretty much do it all within reason (no Grizzlies). Or maybe a .50 is right but then again you wouldn't use it on squirrels. If you were only going to hunt small game, then a smoothbore might be right.
PERCUSSION OR FLINTLOCK
It's up to you. If most of your friends shoot Flintlock, then you would have a resource to walk you through things. I shoot a Percussion and being there is so much to learn, it might be easier. After loading, you just put on a cap and pull the trigger. I have the utmost admiration for those who shoot a Flintlock. To me, that is a real challenge.
WHAT GUN
Once you have chosen the caliber you want, now comes the real challenge, what gun? All I can do is to relate my experience. I wanted a ML that looked had nice lines, was considered a quality gun, had some tradition or history to it, was in good shape, nice wood and was easy to carry. It didn't have to be an actual piece from the 17 or 1800s or had to be totally historically correct. So I wound up with a Thompson Center .45 Seneca manufactured maybe around 1974. The gun us great, but early on I found some problems that as a novice I overlooked. The bore was in great shape however, there was an incredibly fine hairline crack in the stock maybe 4 or 5" long that you didn't notice unless you looked at it in the light. When the barrel was removed, there was an actual hole and an internal split in the stock maybe 4" long in the channel beneath the barrel. Finally, when sighting it in, I found the rear sight bottomed out so I couldn't adjust the elevation any lower. So I had to find a new sight which was almost impossible. Finally, after a month, I found one after much frantic searching. I was charged three times the amount it should have been for the sight because of its rarity. So we have the cost of the gun, the repairs to the stock and the cost of the sight. Oh yes, I had the stock refinished which revealed some really beautiful wood. I think I probably spent on repairs the actual price of the gun. The gun is perfect now. My point being, if you are looking at older guns, you need to get it really inspected. You may not be able to find a part if you need one for an older gun. Check out the bore. Are there any cracks or spites in the stock? Is the barrel rock solid in the channel? Have a ML expert check it out before buying? Just because it is in a sporting good store or gun shop doesn't mean it's ready to go. Now of course, you have current day reproductions such as Lyman, Pedersoli, Traditions, and Investarms. Then you can get custom builders to build you one to your specifications which might be too involved at this point to determine what you really want. Also, you can get muzzleloading kits and build your own? It all depends on time and money. Hope all this helps. BY the way, with the price of the TC plus the all the repairs to it, I was probably around $600 when all was said and done. Good luck.