the game is made to be a challenge, but you dont need to EV, or breed for IV/Nature to win. I beat the game using like 4 pokemon (empoleon, staraptor, luxray and dialga)
IV breeding is for those who want to compete with the best, without it the 1 or 2 stat points will mean the difference between a OHKO and a 2HKO (one-hit and 2-hit ko). If you arent planning to battle competitively (or not on a very high level), IV breeding is a waste of time.
You can battle anyone on wifi, and itll project the pokemon to lvl100 with the stats theyd have when they hit lvl100 themselves. so i could take a party of lvl20s to vs ur 53s and itd be fair
and your torterra looks rather nasty (as in powerful), your level is just a bit low. Cynthia's best is lvl66, and id recommend getting an ice move (ice beam if you can afford it, blizzard otherwise) on your floatzel.
you can breed torterra, you just need a ditto... and a national dex to get that ditto.
how far can you get in the elites? i can see you having issues with aaron, but your torterra should blitz through the next 2 trainers with minimal effort (if you level it a bit)