The Golden Seed will give you an extra Flask charge as soon as you get to the first Site of Grace, which makes it one of the best Keepsakes you can choose at the start of the game. If you’re new to FromSoftware games, I’d definitely recommend going with this Keepsake since the extra health recovery will help you face tough enemies, especially in the early game. However, Stonesword Keys are also extremely useful since they’re needed to unlock certain rooms and dungeons with powerful items inside, so this Keepsake might be a better choice for more experienced players.