Really have no idea how many Gobblers I have called in with mouth calls in the 34 years or so that I have been hunting with them. When I first started there were very few manufactures of them and the reeds were in either smooth or ribbed depending on which Trojans were used to make them. The calls have changed some but the basics are the same.
Single reed call will be the easiest to learn how to use, once you get that down the others will not be that hard.
To call in a bird much of the time only a few yelps are needed. Clucks and purrs can really help seal the deal though. Using turkey calls I have called in Turkeys, elk, bobcats, coyotes, peacocks and axis.
Like someone said while driving is a good time to practice, just not with the Wife.