Took inspiration from smpratte and his scream promos, what cards are you always looking to buy, and why? Reasoning examples could be love for the art, thinking they are undervalued, or still aiming for that hard to reach PSA 10.
For me it’s definitely CoroCoro Shining Mew. Not only do I adore the artwork, I think the actual execution of the card is flawless, the full glossy holo wows me everytime.
Very good question!
Neo Discovery Houndoom holo: favorite holo from the set, favorite art from the set, one of my favorite species, favorite neo set 
Light Wigglytuff/Jolteon: best wotc non-holos.
Masaki promos 
i tried to keep my collecting ego in check and stick to older sets for a long time, but i’ve been collecting some of the full art Secret Rares (trainer, pokemon or otherwise) from the S&M era recently. i don’t play, so i go after aesthetics and we’ve been pretty blessed with recent sets. the artwork and varieties keep coming and there is quality in every set. i’ve been trying to collect the holo energy cards from the S&M era also. those are some of the best looking cards of all time.
Lastly, I’ve been dabbing in promos and special tournament/event cards since I started to participate in Pokemon events more as a volunteer locally. still learning and picking my way through that. Obviously, those big time trophy cards are super desirable but, realistically, incredibly hard to find and even harder on the wallet these days.
Prerelease Clefables
Every artwork I really like has some price threshold where I’ll always buy the card if the condition is alright, even if that’s not below some “market value”. In general that’s mostly Japanese exclusive stuff.
Pokemon
Japanese ex cards and EX-Series holos. They are tough to find in mint condition but the prices are incredible given the artwork and nostalgic value the cards have to me. I have boxes full of the holos and binders full of ex cards and I don’t plan on stopping! Every now and then I’ll get some which are gradable as well which is a treat. Haven’t got around to grading a lot of the regular holos but I have been making some progress on Delta Species holos in PSA 10.
CoroCoro, Natta Wake, Vending, and 1st base.
I have zero attachement to non-wotc era cards…
But I find myself checking every new set and purchasing the female full arts that catch my eye.
Base set holos
Pokekyun, Natta Wake, Team Rocket and Hoopa cards
That’s all it can take to leverage and then suddenly, you wake up from that mindless elitism. Had it occur with me by Rayquazard ☆, Sandstorm Aggron/Aerodactyl ex and the Legends.
Natta Wake set! I’m always buying raw and graded. They are undervalued to me personally considering the enjoyment I get from the cards versus what I pay.
Limited print promos which exist almost entirely in Japanese. Bonus points if they have exclusive art or a holo that has not been reprinted as a set card. Extra bonus points if it’s some sort of event prize with a pokemon I like.
First edition base set. Very nostalgic for me.
Old deck cards. Things like this:
Holon Transceiver
Rocket’s Admin
Cleffa from Neo Genesis
Focus Band
Gold Berry
Oracle
Double Holo Error Neo Revelation Holo Cards
Pop Series 1 holo Tyranitar ex. I got my first one when I was a kid and have collected them ever since. They have a really low psa population and they’re my favorite Tyranitar ex artwork.
Team Rocket Returns ex’s