first to know what gear ratio to use(but this is still not useful to you as of now)
and second to know what class you belong.( one again dont bother.)
on your present state now. just buy a stock motor its a 27 turn its for beginners( just generalizing.some stock motor are so fast too.)
motor limit is useful for your esc. not your radio.
if you check your manual for your esc . some esc has no motor limit and some has.
for example if you have a duratrax 8t esc. the 8t is the hight motor turn it can handle.
if your esc has no motor limit that means??? ......... your right no limit.
motor turn: all motor has turn. that is the number of coils on the armature. the smaller the turn (27t -> 8t) the faster the motor. the higher the turn (8t-> 27t) the slower it goes.