Having competed as a bodybuilder for 20 years, I can tell you that there are many approaches to stimulating muscle growth. But, the most important one is to train "smart". Know what your body can tolerate and push it just a bit further. This does not necessarily mean to lift "heavy ass" weights. However, you must push your body past the point where your muscles adapt to the load that is placed on them. In my opinion, I would use the first set as a fairly light warm up. Enough to achieve 10 to 15 reps. The aim being to warm and prepare the muscle for the load it will receive next. The subsequent sets should place an increasing load on the muscle being trained. This approach should be adjusted in subsequent weeks when you are able to lift more weight. Additionally, you must eat correctly and sleep sufficiently to support the increased demands on your body. Lastly, make sure to stretch the muscle being trained after each set.