So you want to gain muscle size and strength while staying the same weight? Or not getting fat? Not gonna happen. You can’t have one without the other. However with the right programming, nutrition and rest, you can skew the numbers in your favor.
If you’re a beginner, and it sounds like you are, find a program that focuses on strength on the main lifts (squat, deadlift, bench, press). Once you’ve established a solid strength foundation, you can add silly and less silly supplemental exercises while continuing to focus on getting your main lifts up.