I am working on completing my very first master set of any pokemon TCG set.
The set that I decided to go for first was the Pokemon GO set because it was the newest set that had come out when my daughter started getting into Pokemon cards.
A master set includes collecting one copy of every regular card, the reverse holo versions of those same cards, all Pokemon V, VSTAR and VMAX cards, all full art cards and rainbow or gold secret rares. Some sets even have separate side sets for Trainer Gallery cards and promo cards that go along with the set as well and a master set isn't considered to be complete until you have successfully one copy of every single cards that was ever made for that particular set.
As of right now I am only missing 13 cards in total to finally complete my very first master set and I'm probably about $110 away in terms of cost for those last 13 cards but I am hoping to have this completed very soon!