Okay, So, You expect walkthroughs eh?
At level 1-15, Hoping that you have a starter, I recommend a level 20-30 pokemon to help with leveling from 1-15, So...
1, The Easy Way : Train with your level 20-30 Pokemon on random pokemon in the maps, (Tip : Dont kill it until your low level pokemon is out, and ready to go, If you want to be quick about the game, go to medium... If you cant kill it with your lower pokemon, Dont worry, You can die and gain xp if you kill it...)
2, The Medium Way, Bring out your low level, Go to the maps, Train at the place you are good against, (Highly Recommended)
3, The HARD WAY (Also the fastest to level 15) - Go fight the gyms, with ANY pokemon, If its not the low level, Remember to leech with it!
Level 15-50 - Train on the gyms (Medium/Hard, Depending on the gym), To be safe, Sometimes people fight the maps STILL! (Easy, but LONG!)
Level 50-100 - Teach a Pokemon blizzard, and just own giovanni billions of times, It gives you about 5 levels per win after level 80 (Funded), Or you could be the cheap guy, and just fight random elite ppl (Non-Funded)