Which shoulder cut is it and how lean is it?
We grind chuck into burger meat when it's on sale. If you have a lean shoulder, you will need to add some additional fat to get good burgers. Nothing wrong with using some bacon trimmings & ends (you can usually find a 3 pound block of these near the bacon at the grocery store) or back fat (aka salt pork at most stores). Fat is where the flavor is, and if the cut is too lean it can be flavorless and tend to fall apart as the fat helps bind the meat also. The cuts with more fat also tend to be the less expensive shoulder cuts too. If you get a really fatty cut, you can trim some out before the grind also. The beauty of grinding your own is you are in control of the final product. Most people like the flavor of an 80/20 or 85/15 mix for burgers (80% meat, 20% fat, etc...)
As to spices. I usually grind the meat and vacuum pack it "as is" adding only fat if needed and then freezing what we won't use in the next week. That way I have a lot of options later and the ground meat is basically a blank slate to build upon from there. If it pre-spiced it, the spices might not be compatible with the end product I desire to make later. We freeze our ground beef in 1 pound packs.
If you know you want to make up burgers out of the entire grind, no reason not to mix in seasoning into the burgers, it's up to you. A good base combo to start with would be salt, black pepper, garlic powder, and onion powder in quantities to your taste. You could also preform the seasoned patties and freeze some of them if you were not going to use them right away.
I picked up two large shoulder chuck roasts two weeks ago and after trimming of the excess fat and membrane ended up with over 12 pounds of finished ground beef. Looked and smelled better than anything you would buy at the grocery store and I know what is in it. I usually watch the store for items marked way down due to their expiration (sell by) date. You can find stuff 1/2 price at my local Kroger on the last day of "sell by" if it's still on the shelf. You never know what or when they will have this stuff marked 1/2 price, but we check that section of the store every time we walk in and are often treated with a great buy.
