I own several encore rifles, and almost all of them shoot better with different stuff. If it were me I would start by getting some black short sabots from MMP
and some Hornady 250 grain .45 caliber pistol bullets. You can buy them in bulk a LOT cheaper than buying them in the shooter packs. All of my encores shoot this bullet and sabot combo very well. Your powder choice is going to depend on what your rifle likes to shoot better than the others. I have 1 encore that like plain old Black powder better than anything else, but my other 2 would rather have 777. (I tried pyrodex and it shoots well also)
Black Powder seems to shoot better in a bore that isn't as tight on the sabot, but the 777 likes a good tight barrel to sabot fit.
Primers are of no real concern as long as they put good groups together, but I prefer the weaker 777 primers from Winchester.
I wouldn't have any problems hunting with the pellets ( Under 100 yards)but I think if you want to pin point shots, you will want to use measured loads of loose powder. Some guys own guns that will shoot really good groups with pellets, but most of the guys I know, will tell you their rifles shoot better groups with loose.
As far as 777 or Black, or pyrodex. One isn't really much cleaner than the other. All will require you to clean your rifle very well after every shooting session. They will all draw moisture, so you must keep them very dry. By taking a very small amount of all three, and putting them on a piece of glass, and burning each one with a match, you will notice that the Black, and the Pyrodex, will leave a gritty residue, on the glass. The 777 leaves a residue, but it feels like face powder. Very soft and slick. I think this slick residue is why you can shoot more shots between clean out, before it starts to put your sabots in a bind. If you clean out between every shot, as I do, then it really doesn't make much difference.
The main thing with any ML, is consistency in loading. Do the same thing at the same time with the same pressure, every time, and before long you will find the right way to make your rifle perform like you expect it to.