Water

I want to make a simple spherical world which is all just water, also using an FPSController to move around it. How would I make a sphere in which I can walk on and the whole planet is made out of water.
I am a beginner and use personal edition

 

It's too broad what you're asking for. You should divide what you want to do into smaller problems and deal with one problem at a time.

As for how to make spherical water or terrain that's not something that exist within Unity so you will have to figure out how to make your own water shader that can render spherically.

Alternatively you can look into the Asset store to see if you can find anything that helps you create spherical terrain and water.