Crazy J,
My suggestion would be to get a good selection of gloss colors. The basic primary colors (red, yellow, green, blue) are a good place to start, but make sure you have black, grey (light and dark) and silver. Get a few flat earth-tones (brown, black, grey, beige) as these are good for hoses, highlights, and interior items.
As you build more models, you'll get more colors and develop a 'flavour' for what you like and don't like. There are some nice metalic paints out there that look quite realistic. There are also some 'clear' paints (yellow, red, orange, etc) that are useful when painting signal lenses, etc.
M.