Pixelxpixel

I've got 2 level 42 pokemon, so the gym scales to that level. The problem is that I now need to get my gastly to level 42 so it can beat the gym. This would take forever if im stuck farming on the mobs outside the city, all of which are level 14+. I can't use a fishing rod like everyone suggests because I don't have one, and I can't go back to kanto to get one. What am I supposed to do, other than grind for hours.

I'm trying to level my level 60 Ninetales in the seafoam area, but this area is full of water types and obviously it slows things down. Are there any alternatives that provide good xp?