I would use a 22mm sheep casing for the breakfast sausage and a 35mm hog casing for the Italian....as for a a good book, buy Great sausage recipes and meat curing by Rytek Kutas, it's a must for any sausage maker, has a ton of great info and recipes, all around a great read
They got you covered with the books. I use hog casings for breakfast, Italian, brats, etc.
You normally would not smoke any of those. I cold smoke the breakfast stuff for flavor, but that is a different category (and introduces the need to add nitrite cure....a complication you don't need right now).
Most breakfast sausage and the others are served fresh and you really don't even need casings to get started. Grind up some pork and spice it up and you have bulk sausage.
Back that up another notch and you don't even have to grind anything to get started. Buy a couple pounds of ground pork and spice that up. It's that simple.
The Bible is a must for sausage making. I'm also new to the whole world of sausage making too. I have made some 35 lbs already and I have alot more in the works for now. As far as your spices or how too's go to Gander Mtns or bass pro shop or anything like that and you can get the whole package deal. Thats what I did and they will give you the casings (alot too) and the seasoning package already measured out for you. The just follow the directions and whamoo you have some good sausage then when you get the hang of it then you can go to the bible and get you some recipes and go to town.