Your snowdown shop

Out of curiosity, will the discounts in the snowdown shop be at all based on what champions you've played / mastered?

E.g. i already own 1 skin on most of my highly mastered champions and would rather get skins on other champions rather than more on the same champs - should i rank up a few masteries before opening the sales?

Or

E.g. it's based on recently played champions, should i spam play the champions I'd like to get a skin discounted on?

It says personalized so i doubt it is entirely random. Any ideas?