If I were you, I would start on an easy kit. I would start on the new F-105G Thunderchief from Revell-Monogram (or Revell I think). You could also do a Revell-Monogram F-4J Phantom.
Not jet related but Vietnam era is Revells Huey gunship, or if you can find it, their Cobra gunship.
If I were you I would start out with the Phantom. It turns out great, and in my opinion it is as good as the Hasegawa (although money has prevented me from seeing a Hasegawa Phantom.) It is inexpensive and fairly easy (the Revell one).
Academy does a Mig-21 Fishbed, and Hobbycraft makes an A-4 Skyhawk in Nam' markings.
I scored a Heller Cessna O-2 Skymaster from a local hobby shop. But it is a Forward Air Control prop plane. You can build an easy Testor OV-10 Bronco FAC plane. Thats prop to.
Revell makes an F-8 Cruesader, but good luck finding one. I haven't seen one in a while. I also scored an A-7 Corsiar II from the same hobby shop.
All of the kits I mentioned are in 1/48 scale, thats all I build!
Being a high school student that doesn't make to many dills, I settle for the less expensive Revell kits, but work hard on them to make them look good.
Let me know if this helps you, I was once in the same boat, but mine got capsized by armor and I build more armor than planes.
Later,
Chip