I give the first fight to Strange, Time stone should trump the Mind Stone.
Without those stones, I would still think Strange would win unless he for some reason decided to physically fight Loki. The magical effects the sorcerers could achieve, especially with how easily they could seemingly re-arrange the world, make the stuff Loki has look like parlour tricks.
Best magic user? Strange, easily. Though to be fair his photographic memory gives him an advantage when studying spells. But yeah, the sorcerers were shocked he was able to progress so rapidly in such a short amount of time.