I was under the impression that his motivation was pretty much in his name. He wants to be the master of all things and revered as such. Simply to be that.
But on a deeper level, basically, both he and the doctor have a God complex. Both think they are right. One complex manifests itself as the need to be worshipped, the other in the need to guide and heal. Both think the other is completely wrong. The juxtaposing views mutate the mutual respect and love they have for each other to the point where it's closer to hatred.
As as for why the Master would keep on trying to take on earth while the doctor is around or literally make sure he is there to see... if you've been beaten in any game over and over by someone then'll you know the answer.
Earth and human life is a game to the Master... he thinks it is a game to the Doctor to and is confused as to how the Doctor acts like it's not.
I think the best metaphor for them is two leading stars of a band who end up hating one another despite having started close... John and Paul, Pete and Carl, Liam and Noel... ego is nearly always the main thing at play, but it's creative differences in how things should be done that really fuck things up. It's hard to reconcile over clashes of who's vision is better.