I have thought off starting a collection of Le Mans cars at that size (1:43), so what can you (and others) advise, Jager?
From my records, diecast models of approx 1,900 Le Mans cars have been released to date. The question therefore is what to collect and how deep are your pockets.
I think most Le Mans collectors usually start by collecting the Le Mans winners. All 77 winners from 1923 to 2009 have been released by a variety of companies, so that's an interesting place to start and results in a diverse collection. Unfortunately the winners are not always the most eyecatching or technically interesting cars, so you'll probably find yourself drawn to over models.
I know other Le Mans collectors who focus on particular years. I have one friend who only collects cars from 1982 onwards because it corresponds to the first time he attended the race.
An alternative is just to collect a particular marque, such as Porsche (only ~ 400 models), Ferrari (only ~300 models) or Aston Martin (~ 100 models). However one of the things I like about Le Mans cars is the diversity.
In my case, I started collecting winners, this grew to collecting "top 3 finishers" and "anything else I liked". Its the last catagory that's the most difficult to be restrained.
Remember that when you start, there will often be 3 or even 4 companies producing models of the same car in different levels of detail and price. As a rule, the general hierachy is as follows :
Hot Wheels (cheapest / least detailed)
Quartzo / Vitesse
Spark / Bizarre / Redline
HPI (most expensive / most detailed)
Like everything, it often pays to do your research first.