Question about Pokemon training in Alpha Sapphire

Long time Pokemon player here, but I'm new to the idea of competitive Pokemon and all that needs to be done to make a team viable against other serious trainers. Frankly, it's overwhelming and seems incredibly time-consuming, and I was just going to pay someone to raise the team I wanted for me, but then I discovered this Super Training thing.

Is it enough to catch Pokemon with the proper nature and personality trait, then EV train them with Super Training? Or do I need to breed a million billion times to get perfect IV's or whatever? Also while I'm going through the story will my Pokemon possibly get EV's I don't want them to have? In which case should I just get some HM slaves to beat the story, then catch the Pokemon I want to use competitively once I've defeated the Elite Four and Champion?