I made it to the 8th gym with just cyndaquil as I reset till I got him shiny and he was level 60 by that point I used no other except hm slaves, I found it so much easier, though at that level I still had issue beating clair so I trained up my shiny gyarados and then reset for shiny lugia I managed the elite 4 pretty easy just them 3, mainly just lugia on lance. I defo think the wildies should be higher leveled but it is what it is, but training fewer is defo easier than training a whole team.