I collect one of each rarity for Yu-Gi-Oh, including OCG and misprints. Here is my checklist, and here are some outdated scans. Although I still have almost 4k Yu-Gi-Oh cards, I don’t really collect anything else besides this above, unless I find a pretty cool and cheap misprint (a card with misaligned 1st edition stamp that was less than 10 USD arrived today for example 
).
As for your other question: places like E4 for Yu-Gi-Oh instead of Pokémon. Well, there isn’t any place like E4, how could you even think that. 
But Yu-Gi-Oh communities I’ve personally been part of were the Pojo Forum and Yu-Gi-Oh reddit.
Greetz,
Quuador