Onvar true > client -> vceifVar > EXP >= 25 (1 2)
Onvar tru > client > vceModVar > Level Add 1
This would do it im sure. I didnt check but it should be somthing like that.
Your level would add everytime you get 25 EXP. If you add a varfalse event the brick will be able to display a message in bottom print. You can use var replacers in text to display current xp out of /25 points. You could also set different vars for if you wanted to have separate vars level you up such as courage, strength, or spirit