An adjustable powder measure is quite handy. Empty pistol cartridges can make nice measures as well.
You may want a capping tool as the caps are small. The snail type seem the best. Mine is an inline, but it's kind of a pain to use so I usually just put them on by hand. But that's a pain too.
You'll need a cleaning kit. You may want wads, but they aren't necessary. You could do it yourself cheaper in the long run. I bought a punch and a roll of hard felt, and also bought the ingredients to make my own lube.
Typically the most accurate load will be something like 2/3 to 3/4 of capacity, and not a full load. Something like 17-22 grains of powder and a ball. The wads can help take up some of the extra space. The closer the ball is to the mouth of the chamber the better. Some people put dry cereal grains (Cream of Wheat, grits, or Malt O Meal) to take up that space. That's only necessary if you are using a really reduced load because the ball or wad needs to sit on the powder firmly. You CANNOT leave dead space there or it can bulge or even rupture.
You'll need some sort of non petroleum oil. Some use WD 40 or Ballistol. There are many others.
You'll also want anti seize for your nipples. If they get stuck you could be in for a nightmare! You can get a small package at an auto parts store.
You'll want to get some pipe cleaners that have hard rough things in it for scrubbing the back of your cylinder where the nipples go.