How do I make a "Level up" system that gives money when you level-up?

I am currently working on a game and I need a way to give the player a certain amount of cash when they level up.

The way they would level up is by clicking a GUI like 10 times. Then once they've clicked it 10 times, they receive 10 money, level up, and the GUI switches to where they need to click it 20 times, and so on.

I've already created and designed the GUI, but this script is too advanced for me and I hardly know where to start, it would be awesome if someone could help me script this.