>>38942991IVs probably won't make too much difference in a majority of cases, but getting the right natures at least is mandatory, in the breeding department. EV Training is also mandatory.
I'd say go for IVs anyway, at least if you're on Gen 7. Getting 2-3 4V dittos to cover all the stats takes maybe about an hour, possibly 2 if you need to do ALL of the prep required for getting them. After that, breeding for a 5V mon (you won't need 6V nine out of ten times, as you can forego Atk/SpAtk on anything not mixed) can take as little as 30ish minutes.
The whole process from beginning breeding to level 50 EV trained usually takes me 2-3 hours.
I'm really just guessing with those times, I never time myself doing it but I don't get exhausted quickly while dong it.
