Help me come up with an exercise routine

Hi guys. I want to have some exercises to do in my room. It's fairly large and I can fit a few dumbells and whatnot, but currently I can't get an exercise machine.

So far I have push-ups, sit-ups, and squats. I have dumbells but I don't know how to use them atm. If you could suggest a terminal goal with these three, as well as other stuff to do while stationary or with dumbells, I'd appreciate it.

Thanks!

Edit: I am roughly 200lb, 5'7". I am overweight, but I run around a lot in doing daily activities, so I can still move quite nicely. Problem is, my knees are busted up so I can't run. If I could, I wouldn't need any sort of special routine.