To limit the cost of Surge, and make the product last longer, I was thinking how effective the product would be for building mass for a particular body part. For instance, if I wanted to put more mass on my legs, I would use Surge on that particular day only, instead of every workout. Would the product be effective helping to put mass on, in this case, legs? Or would the Surge need to be taken every workout to see results.

you could do this but it may not have the desired effect. Supplementing with surge only on leg days would probably help the legs recover. However, upper body workouts could cut into leg recovery. I would simply do a leg specialization workout for 6-8 weeks while simply doing light maintence work for upper body.