I agree with WJS - a tripod is generally unnecessary for cosplay photos, or for most photos of people. It's important to understand why: You need a relatively fast shutter speed to get a crisp image of a person - even a posed person - and when you're using a fast shutter speed, you don't need a tripod.
For self-portraits, an inexpensive tripod will do. Almost any tripod made in the past couple of decades will be able to tilt up and down - the cheapo non-specialty tripods certainly will. Ask family members if they have a hand-me-down, or post on Facebook if anyone has one they're not using, that they want to unload. Wal-Mart has Sunpak and Vivitar brands for ten or twelve bucks. (at that price, it's not even worth dealing with Craiglist)
There's also the Gorillapod style tripods with the bendy tentacle-legs, those are fun. Looks like there are inexpensive knockoffs out there.
I have a couple of nice tripods, and I use them for the following:
Fixed-camera video - for interviews, b-roll video of a stage performance, etc.
Long exposures of stationary objects (buildings etc)
Panoramas (coupled with a specialty panorama tripod head)
Product photos, where I'm working on very precise composition and lighting
People photos ONLY when I need the background to be absolutely identical - for instance, if I expect to blend several exposures for a "multiple personality" shot, in which a single person appears in more than one place in the finished image.
Just about everything else, I don't use a tripod. Almost never for people and cosplay, and absolutely not at a convention.