Not a big set collector here. So far I’ve only ever completed Vending 1-3, which I was fortunate enough to do by peeling them all off their sheets myself. Then there’s CP3 Pokekyun, which I might never fully complete since Pikachu and Shaymin are just so unpleasantly expensive for modern cards.
Personally I have a more fun time making up coherent “sets” myself, like artist collections or promos with similar releases etc.
1997 carddass baby! the greatest set of all time!
I mean just look at that unique Sugimori art, I feel like I’m in the 90’s every time I look at the cards.
My main goals are every set from base to the end of the ex era, power keepers, fully complete, and 1st if available except for base through fossil. All ungraded, nm for most cards
Before I collected just misprints, I collected complete sets. It’s good to appreciate all the artwork for sure. I started in 2008 (much simpler time lol) so I had the ambitious goal of completing all the sets. In 2016, I finished every set in English from base up to evolutions. I didn’t go for any set in any order. I just traded and bought cards I needed whenever I found the right deal.
That being said, times have changed. I stopped collecting sets after evolutions because the chase was not there for me. I then focused on misprints and error cards. If I started that goal now, it’s totally unattainable unless you have massive capitol. I would pick a few sets you like and work at them. See where it takes you. I have friends that picked 3 sets and they are slowly buying and trading their way to complete it. It doesn’t bother them that they don’t have every set, and it shouldn’t. You’ll just be left wanting more, when it’s sometimes nice to stop and look at what you do have so far.
If I wanted to do sets again, I would either pick my favorite recent set that I didn’t have yet (I really like evolving skies actually) or probably go for psa or cgc sets of the holos from my favorite sets. Majestic dawn, rising rivals, delta species, had a lot my favorite holos. Since I have them already, I would put together a graded set. It’s for this reason that I like errors so much. It’s an outlet to keep collecting, rather than getting duplicates.
Hope this helped a bit. Happy collecting 
I try to collect the modern stuff because it’s fun to open and doesn’t cost too too much in the grand scheme of things. The packs costing around 4 bucks is nice. I’ve been buying singles a lot lately. I usually buy whatever looks cool. I have a bad habit of going on tcgplayer/trollandtoad and searching up a random pokemon. I then proceed to buy cool arts and stuff I haven’t seen before. I recently bought a Japanese shiny gyarados from HGSS era which will hopefully be here soon I would like to buy more of the XY era full arts as they aren’t too expensive and there are a ton of them.
Ereader only
All holos expedition to TMTA secrets in BGS 9 (WIP)
Gym Challenge - find me a set with better pokemon choices for the holos, and cool non holo art.
The only sets I ever had enough focus to complete were a set of #1-151 non-foil Topps, unlimited base and then 1st ed. Jungle - Rocket. Both before and after that I was/am too sporadic to focus on any one set. I did get pretty close to finishing the Japanese vending sets but I fell off towards the end. Now I just stick to particular species or artworks and I also have a soft spot for reverse holos from the ex series.
eseries 
Ive said it before, but I will again; skyridge and aquapolis are the most well-themed sets in the tcg
100% 2 of the best sets of all time. Amazing cohesion and theme for the sets, amazing artwork all around and the best secret rares we’ve ever seen imo.
I’ve only begun seriously collecting with intent in the past year or so. I approached the hobby with the mentality that “there’s always another copy” when it comes to set cards so I put collecting full sets on the back burner and focused on the wonderful world of Japanese promos.
I’ve recently started building a binder set of 1st ed jungle, fossil and (eventually) base as I feel early WotC cards have come down to a reasonable price. It’s been surprisingly very fulfilling and fun hunting down deals on various platforms. I suppose if I’m going to commit to actually getting the original 151 in 1st edition I should probably set my sights on a charizard before too long as the prevailing wisdom is to start with the most expensive card first…
I collect every set. Long-term goal is to complete every English set, with some exceptions like VS series. Building binders and filling in empty spots is part of what makes collecting fun for me.
I don’t collect sets, but rather subsets that I create in my head. For example, I want to own the three chase cards from the three e-reader sets (still working on the crystal zard 
) or I want to own all three gen 3 ex starters from TMTA. or I want to own all cosmic eclipse trainer/pokemon full art secret rares or I want to own all team magma’s/team aqua’s holo rares from TMTA. Or own all Team Plasma B&W full arts. Just weird little stuff like that. I envy those who have binders of complete sets but tbqh, I don’t find too much enjoyment from buying & owning C/UC non-holos so it’s hard to develop motivation to own complete sets.
The Neo sets in general are quite good art wise imo. Plus you get the shinings in Neo Rev/Destiny. I do have a soft spot for the Gym sets though. Love the Rocket’s Mewtwo. I think thats my favorite of the holos.
I once was very ambitious and set up set binders from base set to present day. I finished Base - Skyridge (all unlimited sets - preferred quantity/condition over the stamps). And I have every common/uncommon/rare/holo from the rest of the sets which I keep up with making new binders as they come up. But around the time of Sun&Moon when the number of secret rares began to climb and climb and be increasingly bland (100s of Rainbows) - I stopped wanting every set to be 100% and have gradually opened less and less modern especially with how hard it has been to acquire lately. And that has made my desire to finish all the binders diminish as it becomes an insurmountable goal and I have been adding a lot more to my non-TCG Pokémon collections instead over the last two years. But I still pick up the odd ex card to add to a set when I get the chance! I just find the video games, figures, vintage sealed merchandise, Pikachu plush, and other oddball Pikachu items to be more rewarding as of late
TLDR; Do not recommend trying to collect every set lol
I’ve owned both Gym Challenge and Aquapolis holo sets and I must disagree.
Nobody likes the following holo aquapolis pokemon (except for that 1 Muk collector on E4):
Eh Pokemon Aquapolis:
Ariados
Azumaril
Bellossom
Blissey
Electrode
Exeggutor
Hypno
Jumpluff
Kingdra
Lanturn
Magneton
Muk
Octillery
Steelix
Sudowoodo
Tentacruel
Victreebel
Vileplume
Eh Pokemon Gym Challenge
Beedrill
Ditto
Machamp
Edit: Tongue and cheek post - don’t take too seriously.
@cosrob Pretty much all the ones you listed have amazing artwork including the Ariados no one cares about. If you mean popularity yes there’s a decent chunk from Aquapolis that isn’t that popular. But regardless it still makes the top 3 for my favorite sets
Primary focus right now is on gem mint (PSA 10 & CGC 9.5) English early EX Series holos and exs. I enjoy WotC, too, but EX is just…far and away the most nostalgic and gorgeous era to me.
In addition, I’m also slowly branching out into the exs from the post-2005 sets. I’ve come to realize how gorgeous the exs are from sets like Legend Maker and Dragon Frontiers. So far I only have maybe 5 gem mint exs from the post-2005 sets, though, with my most notable ones being LM Arcanine ex and DF Latias ex. But I very much intend to get more, and eventually maybe even complete a gem mint ex master set.
Haha I personally really like the aquapolis holos and the borders are some of my favs! (Basically guarantees that the lazy pokemon company wont reprint and ruin these cards too *cough 25th aniv)
Azumaril - little fat rat in Venice who doesn’t like that
Bellossom - dancing fella in the forest
Exeggutor - chillin on the beach like a thug
Hypno - frikin eating some dudes dream
Kingdra - one of the best pokemon idc the art
Lanturn - I also just like this fella
Steelix - digging under the ground shot
Sudowoodo - only holo (I think) for sudowood
Tentacruel - crazy cool shot of the squid from underneath the ocean
How dare you