resistance bands

Bands are particularly useful for the core because they force you to stay as tight as possible and help to create tension in your body.
There is a reason that dumbbells, cables, and bodyweight exercises have been around for eons and are still used today—they work.
In all seriousness, the shoulder is a deceptively simple complex of muscles that serve a large array of functions, but here's how to maximize those muscles with only a few exercises.
If you're lucky enough to have enough space to create a home gym then make it the best one you can.