Welcome to the group!

There's no reason why you can't start right where you are. You can always make *any* strength training exercise more challenging by increasing the weight. I started off the same as you and many others on MFP w/Jillian. I slowly progressed through all of her vids, then bought heavier weights and did them again, lol. I would recommend maybe slowly adding other weight training DVDs to your arsenal as well, so that you have a good variety, but can still lift heavy at home. I workout exclusively from home (mainly to DVDs), so it can definitely be done without the gym.

For starters, you can increase weights w/NMTZ (awesome workout, btw), and don't be afraid to go heavy, even if it means you need to pause the DVD for longer rests, or stop a few reps early. You can use the DVD as a jumping off point for lifting heavier, but since most of her workouts are of a circuit nature, it becomes harder to get the muscle building effect w/o proper rest times in between exercises. Once you've mastered the DVDs that you do have, w/higher weights, and have done them every way imaginable, lol, check out sites like collagevideo.com for more strength training DVDs (there are clips and reviews of every DVD, ever, lol). I prefer weight workout DVDs by Cathe Friedrich (cathe.com). Or try some at home free workout sites like bodyrock.tv.

~Kiki