For smoothbores, assuming yours is .62 cal/ 20 gauge.
I'd start with 65 gr. of 3F gunpowder,overpowder wad,65 gr.(by volume, not weight)shot size 7.5,
over shot card or wad.
You will need to play around with your load, some folks use cusion wads as well, I don't.
I usually use 70 gr. 3f, OP...