There's LOTS of stuff you can pick up, but the minimum you'll need is a video transmitter, or VTX, an antenna, a camera to connect to the VTX, and a pair of goggles or box style headset to view it. I've seen guys who have said they could use a video screen to fly with, but if you're doing serious FPV flight like racing, you can't use the video screen - either you'll be looking at the screen and not being able to see the picture well because of movement, or you'll get some sun that will blot out the screen so you can't see it effectively.
Each of those items has its pluses and minuses, with quality, range, and the biggie, the price tag, all focusing on getting you flying. The best advice I can tell you is to research things that you think you want. Start with looking at both the highest and the lowest prices. If you're not sure what a term means or why you might want something like IPD (inter-pupillary distance) in a set of goggles, or the difference between a dipole antenna and a cloverleaf antenna, or what FOV means (it's the field of vision, or how much you can see out of the lens - more field of vision, with a wide angle lens, allows you to see more, but it also makes things look a little more bubbled at the edges), ASK.
I know there are some people who will jump immediately at the cheapest thing because it's the cheapest; others will go straight for the most expensive thing thinking it's the best (and sometimes, it IS), but they don't know anything about that $700 pair of goggles they bought or what makes it better than the $60 box goggles the pilot next to him bought. Or, they'll buy something thinking it's great, and it IS great, but not for the situation they're using it for.
