So I’ve gotten a little out of shape. Not fat. Just lost a lot of muscle. I used to go to the gym 4 times a week on a lifting schedule. I ended up gaining about 20 pounds over 1.5-2 years of muscle. Now I haven’t been to the gym in almost 3 years and I lost all of that muscle. I’m 5'11"-ish and I weigh about 150lbs. I’m more “skinny fat” than anything else.

What are some at home lifting exercises I could do to gain back some of this muscle?

Squats, push-ups, wall sits, crunches, what else? I own two 10lb dumbbells and one 20lb dumbbell.