Most Commander players are attracted to the format because you get to play with all of the interesting cards that arent strong enough to make it in competitive formats like Modern and Legacy
If something feels off about the cards or the seller, walk away
Too many low-cost cards and your deck generally wont have enough power to close out games (unless youve carefully crafted your deck that way), but too many high-cost cards, and by the time youve got the lands to cast them, youll be at zero life
If you and your friends want to change the rules to your liking, go ahead
Impulse purchases, especially at suspiciously low prices, can result in a counterfeit transaction
In my opinion it can be assumed pretty much for sure that the blank spot was where the Ivy promo Pikachu was originally printed on the 1st Edition uncommons sheet (it is known to appear in the uncommons slot)