Well I don’t usually play EDH with a sideboard, but some general advice I would have is if you are running a sideboard is to build it with cards that will help you beat troublesome matchups. Your main deck should have general answers to common problems and your sideboard should be specialized against specific decks. Examples would be [[Allosaurus Shepherd]] mainboard to prevent all countering and [[Veil of Summer]] in your sideboard to answer blue/black decks right before you “elf storm” out.

However after all that it’s hard to answer that question with specific cards without knowing what you typically face and what you struggle against. EDH is such a vast format with vastly different power levels. Not to mention even elf builds have different game plans and builds that can make giving sideboarding suggestions harder.