If you want to spoof GPS, the best way is to use Xposed modules like Pokemon Go Controls but if you want to use the other method of spoofing GPS using Fake GPS apps, you will need to use Lucky Patcher to make the Fake GPS app into system app. Now, this is also a very handy tool for doing many other things with your rooted Android device.
Want to find rare Pokemons in your area but don’t know where to look?
You may want to give the Poke Radar Android app a try as it’s a crowd-sourced map that shows you rare Pokemons in your area using GPS. Whether you are on level 5 or 20, this app will help you get more rare Pokemons so you can level up quicker.