They just sound nice. Mother Oak is 10N per turn [I would prefer every other gem] and Stellar Focus is just 5S, so really pathetic. Maelstrom, Arcane Nexus, Well of Misery, Gale Gate - those are good gem givers
And gold - well, I can buy soldiers for that. And last time I tried to use them against you it was rather sad view.
P.S. My Golems are much easier to kill than wraith lords.