Overall, I don't think you really did a lot wrong, It's just this is absolutely nothing that hasn't been said in every other guide. I see nothing new here. The poor grammar and rambling sentences really don't do it for me either. Sorry, gotta downvote this.

hm... You can smart cast spell (shift+q/w/e/r), so there's no really need to change the command button.
And the build isn't really superior to those who have Archangel Staff. (700+ Ap)

Really, have to downvote this one. First of all, your masteries are misleading for new players, you are ignoring the good parts of Utility tree. No, Improved Flash/Ghost (mandatory for..well..almost all) and ignoring increased exp gain in favor of a pathetic amount of base mana increase. 2nd big thing is that your build isn't that hot. If you go for Tear, you start with meki. However, tear is worthless for Xerath, catalyst is much better since it not only gives lane staying power, it builds into RoA, another big thing missing from your build. Sorry, but can't recommend this for anyone

Thanks! It's a good build!

I won my first game with xerath on this! Nice job!