Here are some of mine:

• The Nova Luna rules seemed so intuitive that I kinda skipped the whole section on how to properly complete tasks. We ended up playing by considering the 8 neighbors including diagonals and no chaining. It kinda worked so we played several games this way before I noticed. The actual rules are a lot cooler of course.
• In the 2p Teotihuacan variant I missed the rule that you are supposed to move the dummy dice after each eclipse.
• In Cubitos for some reason I assumed that the first player die couldn't be re-rolled
• In Evergreen I thought that the first player gets to choose which of the remaining cards they put the leaf token on. This one kinda works too.
• In Tiletum I interpreted the map spot bonus with the "3 heads" as getting 3 Character Actions. The actual rule is a lot cooler since you trigger all Characters in one of the houses.
• In our first couple plays of Orichalcum we refilled the Action Board after each pick. The correct way is to refill only at the end of the round which makes the draft a lot more interesting.