RE: Thomas the train ...where does one start???
We started with a the Thomas Conductor's Figure-8 Set. It's not too expensive and you always can add more track, trains and accessories. I would wait on the table. We don't have one and it's fine. We use the floor. Since he's 3, you might want to get a Figure-8 set and an expansion pack. Currently we have all Thomas track and trains. I know others use generic track with Thomas trains. Our local independent toy store recommends Brio track.
Here are some starter recommendations (plus add your DS's favorite trains :)):
http://www.creativetrains.com/thtaencofi8s.html
http://www.creativetrains.com/thomtanenwat.html
http://www.creativetrains.com/thomtanenfig.html
http://www.creativetrains.com/thomtanenadf.html
Mommy to Justin (13 years) & Ashlyn (8 years)