i have some questions:
1)Do you even know how to administrate l2j server?
2)Can you make your own custom stuff?
3)Can you fix bugs?
If 1, 2 or all answers are answered with NO, then better don`t even start your own server, but you can make it for learning and when you have enough experience, you may even create your own server pack!
For learning i suggest L2jFree server, cuz it is more easy to understand, and you also should take a look at sources!