What you're asking is almost impossible to create. Customs required a fine balance between creativity, logic and a respect for the Narutoverse.
-Creativity: Creativity is good, as long as it don't defy logic and the rules established in the Narutoverse. Also, some members tend to make overpowered customs when using "too much" creativity. You always need to think of a way to counter your custom; if you can't it'll probably get declined.
-Logic: Just follow common sense, don't create customs that grant you instant win, makes you invincible, teleport you...etc
-Rules of the Narutoverse: This is pretty simple again; respect the chakra usages, the elemental weaknesses, the characteristic of your element...etc, and you should be fine.
Furthermore, whether a custom is approved or not is often dependent to the mod checking them. One could deem them fit while another will declined them.
You also have to take into consideration all the customs that were created before your submission (not to copy those).
Hope this helped.
