Melissa, I'm doing BFL for women and am using 5, 8, and 10 lb weights. You'll find in their advice, they want you to do 3 sets and start out with low weight hi reps and move to the highest weight and lowest reps in your 3rd set. So for example, my bicep exercise would be 15 reps on 5 lbs, 12 reps on 8 lbs, and 10 reps on 10 lbs. There is something unique to doing it this way that gets optimum results. You probably will also need to buy a 15 or 20 lbs weight because you will soon see that 10 lb on biceps is too easy and 5 lb as your low weight becomes a feather after about a week!
Also, the big deal is HIIT aerobic exercise. Not doing a steady workout for x minutes, but alternating between high and low. Maybe walk stead for 10 minutes and then 5 minutes of break a sweat power walking, then back to 10 mins brisk, another 5 power, etc. They say this is more effective than walking for 30 minutes every nite the normal way.
What will you see and how fast? Well, I can guarantee you won't see muscle shape. The ladies here will tell you that won't happen until you've achieved significant body fat loss with very clean eating, so that shouldn't be your goal. What you will see very quickly, is a rapidly loosening waist band which feels amazing! Moreover, you will "feel" more than you see. It will feel dramatically easier to get up out of a chair or the couch or your car, when you've been working on your quads (front of thighs). Stairs will become not as annoying to you
, stuff like that.
The stuff you are doing now with biceps and shoulders is great. But the real work comes in working the large muscles of your thighs, legs, and bottom. Those are the super muscles in our bodies and do the most for us. Walking alone doesn't work them enough. In fact, in the BFL book, you should likely start with no weights to do plies and squats. For people over 200 starting out, our body weight is quite often good enough resistance for us.
Good luck & welcome to BFL!