Strength usually leads to increased mass. The more tears you make the fibers of the muscles and causes them to grow larger. That's why I always recommend adding
creatine monohydrate,
Beta Alanine, and
Citrulline Malate.
Creatine increases ATP storage in your muscles so you can squeeze out more reps and get stronger. With strength comes increase mass in muscle as you make micro tears in the muscle fiber. Beta Alanine reduces the pH in the muscle along with H+ and also allows you to do more reps as you're not building up as much ammonia in the muscle tissue. Finally, Citrulline converts to arginine and Ornithine and also helps reduce ammonia build up in the muscle so you have more energy and all three act synergistically to help increase strength and thus muscle mass. You want to be taking 5g creatine per day, 2g beta alanine per day, and 3-6g of citrulline per day, and you ideally want to take them about 30-60 minutes preworkout so they have a chance to get into the blood stream.
Anabolic steroids increase creatine naturally, but with the addition of these supplements you can become a powerhouse and build strength and mass at the same time.
You can research more about the supplements on examine.com. You can use code "starscream" for 10% off any of those products I listed.
Hope that helps,
-SS