There are so many TESOL certificate programs out there. How do I know which programs are legitimate, and whether it's more worth it to take a 20 hour course, 40, 80, or 120? Or is the certificate useless? Do I really need a MA in TESOL to get a decent job. Any advice would be greatly appreciated!

Take a look at http://teflcoursereview.com where former students write about the courses they took. You can get a good idea on what courses are good, bad and so on.

Regarding qualifications, most jobs require a degree and a TEFL certificate. Entry level jobs especially. In my opinion you should only go for higher qualifications after you've had a couple of years teaching experience; otherwise it's too intense and difficult.