Grinder attachment is nice, but the best are the old iron counter grinders. Those babies are workhorses. May as well save space with the attachment though.
Biggest thing is to get the fat ratio right. What kind of sausage are you making?
Every sausage has a seasoning that is distinct you might not expect. Italian sausage, which I’ve made for like 20 years, uses fennel seed. That’s the real reason it seldom tastes like anything else. I also use some cinnamon (I add a pinch) and other seasonings. American sausage uses sage a lot.
For italian sausage, the best is honestly pork shoulder butt. If it’s not fatty enough I’ll grind some extra in with it. You can use natural casings or just form it by hand.