First, Welcome to the Forum. We're glad you joined us.
As for how good you did, I would say that if the bore is in good condition and the lock works like it should you got a very good deal.
Your gun at that price is an excellent starting place into the world of muzzle loading and making smoke.
As this is a Traditional Muzzleloading Forum I have to say that optics were seldom seen "back in the day" and they usually offer no real benefit unless you have severe vision problems.
Most of the muzzleloading guns available today will shoot patched lead roundballs accurately over 100 yards and out to that range the iron sights that come with the gun should work just fine.
Your .50 caliber gun should be loaded with a .490 diameter lead roundball patched with a .012-.018 thick cotton patch.
It will work with either real black powder or with one of the granular synthetic powders.
Don't bother with the powder pellets. They are expensive and they don't work well in side hammer guns.
The powder load you use can vary from 30 to 100 grains of powder measured with a volumetric powder measure. These are available in adjustable styles so you can set it for the powder load you want and lock it in that position.
You will need some percussion caps and your gun will use the #11 size.
If you are going to shoot fairly heavy powder loads (70 grains and above) you would be wise to listen to the folks that talk about adding some weight to your guns stock.
As light in weight as it is, it can give a pretty heavy kick.
Feel free to ask any questions you may have here as long as they don't involve plastic sabots or bullets with plastic on them. Solid copper bullets are also off base.