Something that's essential to growth and gain in any exercise is to have appropriate accessory exercises to assist and complement that exercise.
So, for example, if you wanted to increase your bench press then, yes, you would obviously want to do bench press, but what would actually probably end up being just as important is the OTHER exercises you did, the exercises you did to complement the bench press.
It's absolutely crucial that you do appropriate exercises in addition to bench press if you want to see maximum strength and muscle gain!
So, what I've done here for you is picked out what I think the absolute 4 best exercises to do in addition to the bench press during your bench work out. These are not ordered in any particular order, I just picked out the 3 I thought were the best, and they're all equally important.
#1 - Chin up - This is an extremely powerful and underused exercise. It develops strength in all the areas that the bench does not, and then some. The chin up will really strengthen your upper back and biceps, in addition to strengthening your grip, something that most benchers don't realize is important. By strengthening and building your lats, you're giving yourself a platform to bench off of, drastically improving the amount of weight you can push.
#2 - Dips - When it comes to tricep exercises, dips really take the cake. If you're not doing dips, then you're cheating yourself out of a ton of growth and strength. If you want to focus more on tricep strength, make sure that you're doing closer grip dips. The closer your hands are to your sides the more triceps activation you'll get. As you move your hands out it puts a bit more emphasis on the chest and shoulders.
#3 - Rows in any form - Rows of any shape and size are going to be beneficial to your bench press. You could do barbell rows, dumbbell rows, t-bar rows, anything, they're all going to help your bench press in slightly different ways, but the core principle remains the same...They all build your back. Again, just like with the chin up, this is going to really help improve your bench by giving you a platform to push off of.
I hope this helped you out, and I hope that you start incorporating some of these exercises into your workouts to start seeing improvement in your bench press.