Note that a cosmetic style doesn't usually give you a copy of the card itself, but you only need to get a card style once to apply it to all of the copies of that card you own
Depending on your goals, there are a few ways to approach buying Japanese Pokmon cards
The time you have to wait before you can open the Mystery Box again will be reduced during the event
Treecko Star Ultra Rare, 109/109 Going even further back in time, this Treecko Star card hails from the EX: Team Rocket Returns set, which was released in 2004
The most common are the ones from the standard showdown packs: Captain's Claws/Goldnight Castigator, Fling/Toolcraft Exemplar, and Tormenting Voice/Drake Haven
Id recommend reading through the reviews yourself to see if any of these are a good fit for you