As far as paints go, it's more about the application than the brand name. The ol' "square bottle" Testors paints are probably not the best on the market, but I've used Testors
Model Master and
Acryl lines in many projects with good results.
I don't know if people will line up to stone me for saying this. . . but I've never been a huge fan of Tamiya paints. :confused I feel their consistency is just too "thick." At least for brush painting. I've never tried to airbrush with them.
For airbrushing, and brush painting, I
really like Floquil and Polly S. (I believe they are made by Testors also.) The Floquil colors are enamels, and Polly S are acrylics. I've used them extensively for several 1:1 Boba Fett helmets. They airbrush great, even with no thinning, and they're pretty pigment heavy, so it's easy to brush them on too.
Another great airbrush line is Vallejo. They're designed specifically for airbrush use, and the color range is really wide.
If you're looking for inexpensive kits to experiment with, I'd say look at some small tank/AFV kits. Pretty much every hobby shop on the planet carries tanks.
Or you may still be able to find some of the rereleases of the AMT/ERTL Star Wars kits to practice "sci-fi" weathering. The X-Wing or Snowspeeder are good to try different methods.