I have a good way to raise your pokemon, it's got some cheats involved but it's worth it, you can have a superstrong team from the first time you set foot in a gym, here goes...
Step 1. Use the Pokerus code 0101fbdc
Make sure all your pokemon have it before you continue
Step 2. Use a code that will allow you to buy LUCKY EGG from the pokemart 917eF2D0
Step 3. Let your Pokerus infected pokemon each hold a LUCKY EGG.
Now calculate: POKERUS increases your pokemon's growth rate by 75% (i.e. say you face Falkner's pidgeotto, you normally get somewhere around 200 exp for knocking him out, with pokerus you will get 325 exp, combine a lucky egg and you'll get 587 exp. Overall your pokemon's growth rate has increased by 125%
P.S. Keep the pokerus code on if you don't want it to leave.
Get Your Game On!