Collecting automobilia encompasses a vast array of subject material not only cars, but motor sport, vintage motorcycles, motoring literature tools, garage signs, and racing car spares to name just a few:
With such a range available it is sensible to try to stick to one or two fields of collecting, say Lotus, Ferrari related.or Formula One, and Le Mans  items. 

I tend to go for anything motor sport related from the pre 1980 period
Race programmes are a fascinating subject as they take you right back to the day, with period advertising and details of the star drivers. Autographed programmes are particular prized. There is also a strong following for collecting old motor sport books, car brochures and catalogues In general modern automobilia items do not fetch high prices unless linked to names like Ferrari. or Bugatti.

Pre war items are now very much in demand many are now rare and hard to find as they had no percived value at the time many items were thrown away.

Condition is very important as with any collectable Above all you should always collect what you enjoy not for its perceived investment value . The thrill of the chase is always  what drives collectors on!