Those of us who have used GPS Spoofers and other hacks to rack up experience level and fill up our Pokedexs have been fortunate so far. Niantic has been soft banning folks for a while now. What normally happens with a soft ban is you will be able to navigate through the game, but any Pokemon you try to catch will instantly run away. You will also find that PokeStops are totally empty. This is a major drag, but eventually the soft ban will wear off. It generally takes anywhere from 10 minutes to a few hours.
Recently Niantic started permanently banning some people using GPS spoofers and other cheats and hacks. Permanent bans can be avoided. Here is how.
1- Stay In Your Local Area
The first and easiest way to avoid bans is to simply stay in your local area. If you are using a GPS spoofing app like Fly GPS staying in your local area will keep Niantic from seeing you are spoofing your location as you could genuinely drive to locations close to your home. This means looking down your GPS spoof and launching the joystick on your street address or near it before starting. As long as you stay within a 5-10 minutes drive from your home you should be fine in theory.
You are most likely to get banned if you are teleporting from one location to another location far away so if you live in California and transport your GPS to NewYork after having opened the app in California you run the risk of getting banned.
2-Use A Root App Like Mock Mock Location
You can use an app like Mock Mock Location to hide the fact that you are using a GPS spoofing service. This app is available through the Xposed Framework Installer as a module. You will need to be rooted with Xposed Framework installed on your device.
3- Use A VPN
The game sends your IP adress info to Niantic to improve location. If your GPS is set to say New York but your IPS is in Japan you will likely see a ban. Use a VPN to make your IP address show the same general location as your GPS Spoofer.