How do I Make a level system?

How do i make a level system?

like i start level 1 then after 10 kills my xp goes to 250 then it goes to level 2?

Just like you explained. You need variables, that change, depending on the experience player gains, depending on the enemies he kills.

It can get complicated pretty fast to balance the whole thing.

can u make a capx?

Here's a capx of an example project. I'm working on a project that involves a lot of leveling. The basic mechanics of leveling are easy, but as was mentioned before, thing's get really tough to balance once you have multiple things going on. Let me know if you have any more questions.