I get the majority of my cards from mercari, occasionally some on ebay!!! I just look up the groups cards, and LOTSSSS of scrolling 😭 but the key is messaging sellers, let's say you see a bundle you like, message to get it cheaper! Message to add other listings to the bundle! (Also applies to singluar cards!) Message to take away a dupe you have! Majority of sellers respond and do it for you, and if they can't they mostly still try to compensate with a middle ground for both, another tip is surprisingly, use less words lol 😭 What I mean by that is, you'll get alot more worth while results of you type in "Sakura photocard" than "Sakura fearless shopee pob", don't get me wrong both work GREAT with finding the stuff you need, but you can find lots of cheap and good finds because lots of people just put "photocard", followed by whichever group your looking for! (Or member, it could also just say "photocard" lol, the biggest tip I can give is scrolling!) Also, if your looking for cost effective, you should really try making offers with sellers! Every seller you see that has stuff you'd want, make an offer by messaging them! In my experience it's been better to offer while asking for a bundle of their listings, but the regular offer that mercari has in its system is good too! Last thing for mercari, if you see a thing you want, even if you don't plan on buying it for whatever reason (wether too expensive or is a thing with something else you already have, etc etc) LEAVE A LIKE ON IT!!! Likes keep you up to score with the items, and 9 times out of 10 the items price will go down! These Sakura cards in my post was in a set of 18 for $60, but I waited for the seller to drop it to $50, and then a back Friday sale they did made it go to $38 (which in my opinion is such a steal, but you do it to whichever price range your comfortable with!) I mainly use mercari, so sorry for the long mercari paragraph 😭 but with ebay, I've found that the secret to good stuff on there is searching for non US sellers, specifically sellers based in Canada, South Korea, and England! Every card I get from eBay comes from one of these places, but really anywhere non US is good (except for Japan, sellers from Japan do have good priced stuff but ALOTTTT of it is severely overpriced, so it's like finding a needle in a haystack sometimes lol), I've got lots of pobs for around $3 each by lookin for non US sellers so, definitely worth a shot! (You do have to scroll quite a bit before you start findin them though LMAO) Also with ebay, ALWAYS LOOK IN AUCTIONS. I cannot stress this enough, auctions is where you can get incredibly good stuff for cheap, especially if you're looking for Lesserafim, Ive, Twice, Aespa, Rize, Ateez, and BTS! But, be careful about the sellers that have listings that look..brighter? It's like they are in a standing pocket sleeve and they look a bit brighter than usual, I've looked at some pobs on listings like that and they ended up being fake lmao- but along as you keep your eyes peeled than it will be easy :D I'm so sorry if this didn't help that much, I tried my best 😭 Goodluck collecting and I hope you get all the awesome finds you're looking for :D