Levels don't provide many advantages, unless you'd like to monetize your content(?) or you're after collecting
ranks and class names. c:

(
more about rules for PMC)
You see that emerald I just gave you? Well that's how you get them! Commenting on submissions
and through creating posts in forums (
not to be confused with wallposts!
Wallposts only earn you likes); you'll have to make some good comments if you want to be an emerald collector, or just keep the fun going in the forums section.
And for page design; my two-cents would be to keep things neat - make it easy to find any information that you feel is relevant. That'd be it, do/add anything else.. "good" advice for profile design means something different to everyone, and aesthetic always boils down to the individual.