Personally, I don't know if there's just one way to answer this question. I think it's great to continue to challenge yourself. Playing simple root notes may seem simple, but it's also a good way to work on your rhythm and timing. The harder stuff, like Chili Peppers, is a good challenge, but may not be practical at this point.
I think it's great to listen to the harder stuff, and great to try and challenge yourself by trying out some of the licks, but that should be a small part of your studies. I strongly encourage you to seek out a teacher. If you can't find an affordable private teacher, (try music store postings of
http://www.harmony-central.com), also check out local programs at your school, or even junior colleges in the area. Many times you can get in on one of their programs, depending upon their rules.
The foundation really is in theory. Learning scales and arpeggios (chords) could not be more important to a bass player. Building a solid foundation there will help you understand how the more difficult bass lines are produced. Of course, then you've got ear training, rhythm training, technique.
I don't know if this is too broad? Does this help at all?
By the way, I'm sure I'm leaving a lot out, but I'm sure everyone else here can help me out.