>>52728462cont.
Some incidental e-Reader stuff I won't price but useful and fun to collect:
Berry Fix Program - one of the various attempts to fix the Berry Glitch in Japan for RS, not hard or expensive to find.
Pokemon Pinball RS - 5 cards, one easy to find, three really hard to find, the last nearly impossible to find as it shouldn't have been distributed but somehow did. All they do is unlock cheats like extra lives and stuff. The last, impossible one made it so the Johto Starters were catchable.
Pokemon Channel - handful of cards for adding new patterns to Smeagle Paint, you'll find these randomly in both Japanese and English, and I believe they're cross-compatible!
There's a bunch of random non-Pokemon stuff that you can find for e-reader vastly cheaper for the most part. There's a Mario Party card game meant to be played with multiple people called Mario Party-e. Super Mario Advance 4 had a bunch of level and powerup cards and while there's a fair few rare cards in the set, it's vastly more achievable to complete, though it does have one more near-impossible card to find. There's also a whole Animal Crossing set in English and Japanese, and some Japanese only sets for Megaman Battle Network and F-Zero and Pikmin.
I don't know how EASY it is to collect cause I haven't started, but I bet you could find a lot of loose singles of the old TCG cards with various dotcodes at very reasonable prices. Something I recall is that the holos and valuable cards of the set DIDN'T have dotcodes (probably for damage concerns), so there probably aren't a lot of scannable cards that are prohibitively expensive to find, you'd have to ask a TCG expert.
pictured: a rare photo of the extremely rare cards that changed hands on Discord a couple years back or something