Hey Kalibi,
First of all, you should be offering some kind of payment. Java and plugin development can take years to be really master, and making plugins takes a lot of time and energy. Can you give any good reason why a Java dev would want to stop making money and take time to help you? You didn't really give anything reason like that in your post.
Also, I'm a bit offended that you want 17+ aged teens. Is that because of the nature of your content, or because you don't think younger devs can make good plugins? I've worked for three different servers in the past, made multiple minigames and gotten paid for all at the age of 14. I take pride that I've nearly mastered the plugin API.
Lastly, if you want anyone to join, especially adults who need to support themselves with current jobs, offer at least $15/hr. Check out the SpigotMC forums under the Server Recruitment section to see what other people are offering.