Hello Malia,
Welcome to APUG. I'm sure you're going to get a ton of advice from lots of people here, so let me get my 2 cents worth in first. At this point, I would consider playing around with some more toys for a little while...they really drill composition and lighting into your head due to the lack of shutter and aperture options. And of course, they produce images that digis just can't...for example, I have a Diana myself, and I just ran a couple of rolls of Kodak Ektar through it. Fantastic stuff--the bright color really adds to the Diana's photographic motif.
I would also strongly consider playing with a Holga, if for no other reasons than it can shoot truly a full-frame 120 image (unlike the Diana which crops), and it leaks more light than the Diana, so it creates even more of that toy camera atmosphere. Also, the Holga's lens is a slight wide-angle, whereas the Diana is nearly a "standard" lens.
There have also been some new additions to the toy camera family in the last couple of years. The Blackbird Fly is an honest-to-goodness old school TLR that shoots on 35mm film. The Golden Half 1/2-format camera is a tiny little thing that shoots 72 images on a 36-picture roll of film. The Holga now comes in a stereo version, as well as pinhole. So, your options are wide open.
I would also advise that whenever possible, shoot in black & white if you can. B&W lends itself to toy cameras really, really well, especially with all the light leaks some cameras produce. When you combine B&W toy camera images with techniques like lith printing, creative toning, or wilder stuff like chromoskedasic, the images really take on lives of their own. Well worth the extra hours spent in the darkroom.
When you're ready to move beyond the toy camera world, I would recommend picking up a good used all-manual camera. There are plenty out there, so if you're patient and selective, you should be able to find yourself some good deals. Classic Nikons, Canons and Pentaxes (I personally love the old Spotmatic line) are almost always good bets, since many of them were built really well, and there are plenty of lenses available out there for them. Or if you want to go larger and have a little more money to spend, it's hard to go wrong with a used Mamiya or Hasselblad...there are even some affordable Rollei's to be found. Or, if you're interested in something more off the beaten path, you can check out places like this:
http://www.certo6.com/
Whichever way (or ways) you choose to go, I wish you luck, and hope that you choose to take yourself in exciting new creative directions.