If you have an Android tablet I would recommend you to buy those. They are refined ports and they work really well with the touch system as they are turn based. Begin with those they will take you some time to finish.
You can play all FF from 1 to 6 on Android and iOS.
After that you can begin the 3D era of the games. 7 to 9 are on Playstation 1. FF8 has been released on Steam for PC as well. I recommend you a PC emulator for 7 to 9 if you don't own a Playstation.