Squats with dumbell. How does that work exactly?
But seriously, body weight exercises are good and you can actually do a lot with just a dumbell, but how will you progress? That way you'll hit a plateau pretty quick, your muscles will get accustomed to the same exercises and weights, you're gonna need to force them with something harder. For example one doesn't need to do over 30 push-ups, anything over is just gaining endurance, not muscle growth. How do you expect to overcome that?
But all that aside, you really should get at least one more dumbell next. You can do a LOT more with two dumbells. Than in the future a barbell would do you wonders...squats, overhead press, deadlifts, etc.