I actually collect less than a year ago. Due to the current market I can’t keep up with all my collections at the same time (what a surprise haha 
). I’m glad to say I’ve been able to finish some of my collection goals, so I can focus more on one of my main collections.
My main collection is of course Pikachu in all languages and variations. When I came back collecting in 2015, this was the collection goal I had set my eyes upon, and right now I own 1474 unique Pikachu cards, with 42 more incoming, and (apart from the upcoming Vivid Voltage set) just 22 more officially released Pikachu cards left to find, and about 25-30 more unofficial ones I’d like to add as well. So not too shabby, if I say so myself. It’s hard to keep up sometimes, especially with releases like the upcoming Vivid Voltage set which contains four Ultra/Secret/Hyper Rare Pikachu cards, multiplied by 11 languages, which cost A LOT of money in total unfortunately… In addition, there are quite a few country specific releases every now and then. I for example have two Spanish Pikachu cards incoming; one exclusively released in Argentina and one exclusively released in Mexico. And I’m also still looking for a Spanish Pikachu exclusively released in Chile… All pretty tough to find if you live in The Netherlands (Europe) and don’t speak a single word Spanish. 
Another goal of mine is also all languages and variations, for my favorite Pokémon Seviper. I’ve started this collection 3.5 years ago, and I’m happy to say I’ve 100% completed it since this part Monday, when the last two Indonesian Seviper cards arrived from my Indonesian contact. The Japanese unlimited edition World Championship Pack Seviper and Battle Frontier cards were the main bottleneck for this collection, though. But I’m happy to say this collection is now complete. 
Here some pictures, excluding the Japanese unlimited WCP and two Indonesian Seviper cards, for which I still have to update the scans.
My third collection goal, which is currently 100% complete as well, are all English and Japanese exclusive Full Art Supporter cards. This collection is amazing to browse through in the binders, and I’m so glad I started this collection two years ago. Right now it’s primarily just keeping up with new releases, and hoping there won’t be any more expensive Japanese exclusive releases in the near future. Here some pictures of my completed collection.
My fourth collection goal, which is almost complete, are all raw, sealed, and graded Moltres WotC #21 artwork variations in all languages. This is my favorite artwork of all existing Pokémon cards, so I have this little subcollection dedicated to it. A few months back I’ve been able to find the Australian sealed variant with Game Boy Color insert as well as a sealed unlimited edition Japanese Pokémon Web booster pack containing the Moltres, so all I’m still missing is a 1st edition Japanese Pokémon Web booster pack, and perhaps a CGC-10 graded English Moltres, to finish this collection goal. Here some pictures of my collection thus far.
My fifth collection goal, which was finished, but with the latest release not anymore, are all Ancient Mew cards as PSA-10. There are right now six different Ancient Mew variations. Here are the four oldest ones from pre-2001 in PSA-10. And here is the Japanese ©2019 version which I graded a bunch myself. So all that’s missing now is the Korean ©2020 version, assuming PSA will grade them that is. If not, I’ll go with a CGC-10 instead once they offer grading of foreign cards. I currently have two Korean Ancient Mew cards incoming to try and complete this sextet in the future.
My sixth and seventh collection goals are both put on a hold for now. I collect the entire National Index, including all Pokémon forms, gender differences, and shiny Pokémon. Here my collection thus far. I have yet to add the entire gen 8, and all forms/shiny Pokémon released during the Sword & Shield era, but I won’t do this anytime soon. Another collection of mine are all Yu-Gi-Oh rarities for the Japanese OCG, Korean OCG, and English TCG, including misprints. Here my collection thus far. I did recently add three very rare misprints, and I’m still on the lookout for a fourth. But apart from that I haven’t keep up with new releases after the TCG 10,000 Secret Rare was released, which just like Charizard cards was 1000+ USD from day 1 of the release… 
So both of these collections are on a hold for now, and no idea when I pick them up again. Given today’s market, this Vivid Voltage set, and the upcoming 25th anniversary which will be packed with Pikachu releases as well, I doubt it will be anytime soon or at all…
So yeah, as I’ve said, I collect too much at once, haha. I’m glad many of these goals are now finished though, so I can focus everything on Pikachu (and keeping up with new releases for the FA Supporter and Seviper collections).
All these collections can be found as lists in my signature below.
Greetz,
Quuador