While commons might not come to mind when you think of valuable cards, quite a few are worth a pretty penny, particularly those from older sets
However, if a player is new they know nothing about eternal formats anyways
As for the other three (Evolution SageEvolution Sage, Metallic MimicMetallic Mimic, and RealmwalkerRealmwalker), while they're creating synergy with the deck, I would have preferred something a little more oceanic, or at least from Ixalan itself, like Roaming ThroneRoaming Throne, for example
Erika's Dragonair is a Rare Holo - (Stage 1) Colorless type Pokemon card from Gym Heroes
If you have none or very few of these cards (and minimal other creatures), your prioritization of them should continue to go up as it gets later in the draft