I have this plugin edited to work like this
Its play time based. When they first join the server they are Level 1, after x
amount of time they level up.
Each level is configurable, you can set how many store credits you want them to be rewarded with, which admin flag you want them to get on each level up.
Also it plays a cool lvl up sound.
Also there is additional !levels menu where it opens up and you can track what/when you are going to unlock in future (also completely configurable). And it also says your current total play time and when you type !nextlvl it says amount of time needed for next level.
Iv set it so people that reach level 18 and lvl 20 get free admin/admin+.
Until those levels they unlock VIP, modules inside store plugin etc.
Their level is also shown in scoreboard next to their name aswell as in chat when they type.