ya, Im personally not a big circuit fan, regardless of the situation.
Personally, if you make sure your diet is spot on that will help you lose body fat, but at the same time start building/maintaining lean mass, thats the way to go about it in my opinion.
Circuits are only used in certain cutting situations, I just think you need to get on a basic weight training and cardio routine and make sure your on an appropriate diet! I think you'll be fine for your USMC tests bro!

Good luck