You will find the learning curve getting into muzzle loaders is steep.
I started in the late 70's.
I am still learning.
You can lessen that curve by starting with a percussion rifle as stated earlier.
THEN if you like it, step into to a flintlock.
The nuances of operating a flintlock is something you just don't jump into.
and even with years of experience in caplocks, unless you have a mentor to show you what NOT to do, you will probably get frustrated quickly.
That being said, even after 30+ years of muzzle loading, (and shooting most anything else with a trigger) I still prefer to use percussion.
Not saying I don't know how to make a flintlock reliably fire, i just prefer the percussion.
Which ever you do get first, take it to the range, try different loads and projectiles.
Remember, the max loads are rarely the most accurate, a good hit in the vital areas of an animal is better than a miss with a lot of smoke and recoil.
Since you are "handloading" each shot, it is all about consistency, using the same powder charge, same patch thickness (or sabot if you are using modern projectiles in a fast twist gun), same seating pressure, are you going to be shooting from a clean bore? or a fouled one. (it does make a difference).
Muzzle loaders are not like a modern rifle where you bring it home, shoot it 3 or 4 times to zero it, and then throw it on the rack until deer season.
Each gun is different, they have their own personality, their likes and dislikes.
I have 2 .50 cal Hawken rifles, 1 by CVA, another by Thompson Center.
The CVA is most accurate with 55gr. of FF with a .010 patch and a .490 round ball.
The TC likes 70gr. of FF with a .015 patch and a .490 round ball.
Go above or below these powder charges, and the groups start getting bigger.
Good luck, Let us know which way you go, and how you do.