The best approach will always be based upon science.
67-85% of your 1RM are the ranges one should be training at in order to increase muscle size. The repetition ranges are 8-12. These guidelines along with eating the proper amount of macronutrients and proper rest will put on you the path to hypertrophy.
Speak with your trainer. I am sure he/she will be able to assist you in reaching your fitness goals.