Yesterday, i found a server called Challenge. You go in, and can either freebuild, or do the Hard but fun challenge, jumping being the main thing, though there is a bit of puzzle in one bit.
The first time, I had to get help every now and then, but the second, I did it all! The staff are really nice, always willing to help you, though you can get banned easily: Dont ask to be an admin, Dont cheat by using ghost bricks, make sure you read the rules when you enter.
So if you see the server Challenge, with Willis, Mino, Ukkeli, or a sign that says about a ruby, have a try!