I'm in Nimbasa City and my highest level Pokemon is only level 24! I'm incredibly scared to go and train in the Desert Resort and places like that since my Pokemon have an incredible weakness to Ground (I'm planning to fix it, you'll see how when I show my team), and Routes 5 and 16 have trainers that are a bit too tough! What can I do at this point?
BTW, on my team, I have a Flaaffy level 24, a Magnemite level 21, a Pignite level 21, a Grimer level 20, an Onix level 19, and I'm planning on getting my hands on a Vaporeon.
Try training in the Virbank Complex. Despite the fact that with the Pokemon you have aren't good match-ups to the wild Pokemon there, their the strongest their that your Pokemon can handle. Also try the Castelia Sewers. You should come out with good results.