Maybe look into Kettlebells? I have a 15 lb kettlebell and just do as many swings as I can (watched videos for proper form) until I feel like I can't handle it anymore, a few times a week. It's not much, but there are a lot of other exercises you can do with them, and swings are a nice way to build up muscle when you have little to start with (as is my case heh). 15 lbs is the recommended starting place for women, I believe. 25 lb for a man or a semi-fit woman.