Ok, it seems you really don't understand the way KORG keyboards work.
You have programs and combis, and you can edit and overwrite ANY of those.
If you need a specific number of sounds for live gigs - the best way (and the easiest) is to store them in order one after another.
The only problem with the X50 is that there are no free banks - so you will have to overwrite factory preset sounds!
All that has nothing to do with favorite sounds - and by a simple push of the INC button you will get the sound you need.
And if you really need a "favourite" group of sounds - like the sounds you use most often - just store them in a user cathegory. Once again - pressing the INC button you will go through those sounds while the user cathegory is selected.
It really can't get any simpler than that