i got back into working out in a gym last year, and i was really surprised how much the science has changed in strength and conditioning. In a lot of circles, cardio is getting really frowned upon....basically you burn calories but youre really just breaking down your system. You may want to look into tabata protocol training......its hard but i did have a lot of success in a short amount of time with it as far as conditioning goes. With my limited knowledge i think id recommend tabata, sprint training and some weights......and not so much the long drawn out cardio unless youre just trying to burn calories for the sake of burning them.