Go to Track of the Wolf's catlog on line, ( listed in our Links) and go to their ammunition components section. They show life-size pictures of the wads, and cards, and give information on their thickness, and diameters for each caliber or gauge.
As for starting loads, here is some information from Hodgdon's Data manual from many years ago:
12 gauge, using FFg powder:
2 3/4 drams(76 grains)with 1 1/8 oz of shot, will give 1062 fps MV.-light load.
3 drams( 82 grains) with 1 1/4 oz. of shot, will give 1035 fps. MV- medium load.
3 1/4 drams(89 grains) with 1 1/4 oz. of shot, will give 1050 fps. MV.
You should also look at Bob Spenser's Website, Bob's Black Powder Notebook,
http://home.insightbb.com/~bspen/ Which has a lot of information in a couple of articles on how to load shotguns and fowlers. Pay attention particularly to the advice given by V.M.Starr in his article on the second page. He covers a wide range of shotgun gauges, and gives good advice on which gauges to use, and why. Bob's own article covers loads for his 20 gauge fowler, and is absolutely Excellent advice.
You will find equally good advice under the Smoothbore topic here on the forums. Go through back posting for a year or more, and you will learn an amazing amount of information that will answer all your questions, and save you hours of work trying to come up with a "better load". Then, read a year or more of postings under the Traditional Hunting topic, to find out what members have been using to actually take various game species. You will find information- and often pictures-- of game taken from varmints, and rabbits, on up to bears, and moose.