I read on a walkthrough that it is recommended that all ur characters are at the end of their sphere grid. I was just wondering where the sphere grid ends for each character?

Usually there's an ability sphere then a lock sphere leading onto another's sphere path. This is for the Expert Sphere Grid, I suppose, because I have't used the standard since my first play-through.

Is the expert shere grid on the International only, because I have never heard of it?

You should be able to find the answers to all your questions in this (Thread 11098) thread.