Choosing the right platform is one of the most important steps that you will take and agonize over.
If you have luxury of owning multiple vehicles to cater to all your racing interests, and more, then this is not a complex matter. But for majority of us this is a dream. So choosing a right vehicle platform becomes a complex and important starting point.
But before we get in to matter of choosing platform we need to first need clearly define what motor sports you will participate in. Track race? Rally? Drag? Street Race? Autocross? Sprint rally? One or many of these?
This is not an easy decision for a layman who just wants to go out and “race”. The practical reality of budgets, time and location play spoil sport.
My advise is to enter in to cheapest form of motor sports and test the waters. Over the years I have seen many people who considered themselves “fast” drivers humbled at competition. So I always advise any enthusiast to first start off on a Autocross or Sprint rally in a standard off the shelf non-modified car.
Even if you do not end up winning examine the results carefully and compare your performance vis others in the same class of vehicles as yours. Check and reason your timings before you take serious plunge of modifying you vehicle.