Hi Michael, welcome to Diatribe! We'd really love to have you along to one of our events to help you make up your mind about larping - I can relate to (once) being a poor high school student nervously eyeing up larp, when I first got into larping I had to choose between larp and Magic the Gathering because I could only afford one of the two hobbies! We're pretty keen to help newbies out though, so if an event catches your eye, the community is pretty good at helping you out with costume or anything like that.
Definitely consider signing up for the May game of Teonn (teonn.nzlarps.org or the forum on Diatribe) as crew - it'll be something like $40 which will include all your food, accommodation and costuming for the weekend, and you'll be in the care of some sterling Game Masters and fellow crew It's possibly one of the most affordable ways to try out high fantasy larping.
Otherwise, keep an eye out for one-off events, which cost between $10-$20 a pop for an evening's fun, and come in a variety of genres. Don't be shy about asking questions, and don't ever let not having a costume stop you, someone'll have something they can lend