I would include the skin with sausage meat. If the turkey is fat, you can probably add all the turkey fat and not need to add pork. The pork is to add fat.
I save the drippings when I cook geese and ducks and put that into sausage, but you have to plan ahead to do that, and if you are making sausage right now, it's a little late
By the way, if you are making link sausage, you really do need the proper amount of fat, but if you are making bulk sausage, it will work if it is quite lean. If it is really lean, then you might need to add a pat of butter to the frying pan so it won't stick when you cook it.
I like bratwurst on the grill, but it is a tricky sausage to make. So are hot dogs. Homemade dogs are wonderful, but brats and hotdogs are emulsified sausage and require a sausage stuffer. Not a beginner's project
I do bulk chorizo to make breakfast burritos with and I make an Italian sausage to go on pizza or to be served on a bun with sauteed peppers and onions. My family is crazy about Italian sausage with peppers and onions.
Bulk breakfast sausage is really easy to make (like Jimmy Dean sausage patties) and it's good for breakfast sandwiches like McMuffins.
I am still testing recipes in small batches. Not all recipes are good and many of the recipes need seasoning adjustments. I'm not doing a full batch of sausage links with 20 pounds of meat until I am 100% certain that the flavor is exactly what my family wants.
I make sausage all the time, using turkey, chicken and beef. I use seasonings from Deep South Blenders, that my butches sells me. I do not eat pork, for health reasons, so I use a nice untrimmed chuck roast with my poultry meat. I skin and debone, then cut it into strips about an inch wide, so I can put them into the grinder/sausage maker together, so when the sausage goes into the casings, mixed. I also use the turkey and chicken fat, because it keeps the sausage from being too dry. I have always cooked the sausage i made, but we just got a smoker and next time I make sausage, I plan to smoke it. Packets of sausage spices and seasoning will make 25# of sausage, but you can shake it up good and weigh out the right amount for the amount you want to make. I like hot, mild Italian, hot Italian, green onion and Cajun.