Wow.... So I just checked out your server and I don't know what you are using for the registering plugin thing but it freaked out and kicked me 3 times. Probably why no one is staying on. After about a minute it warped me to some weird hole in the ground and I couldnt move. Tried to register my password and got kicked. You need to test your server with a different account to make sure things are working...
You need to install plugins like essentials, group manager, and grief prevention. Just examples, there are many different plugins you can choose from. You can check out my server Play.BeyondTheBlock.Net to get an idea. It is pretty new and I don't have many players so you can just go on there and check it out. You can also just message me. I am pretty new but I have spent a lot of time setting up different plugins. So I have a decent idea on most things.