[724Skinsfan]

Firming up and improving cardio? I'd say 3 sets of 15 reps will help in that regard. There are so many philosophies out there about what's the best workout. It all boils down to resistance. Heavy resistance over shorter period of time will increase your power/mass. Lighter resistance over longer periods of time will increase your endurance. In my opinion, your biggest enemy will be boredom so change your routine a little bit once every 4 -5 weeks. Also, set goals for yourself and keep track of your workouts in a notebook. Sometimes you need these psychological tools to keep focus.

Also, your diet plays a big part in toning muscle, not as much if your bulking up.