What would you guys recommend a F2P save their gems for? What’s the best bang for the buck?
Atlantis is intrinsically a “better” deal, because it has better probabilities on 5*, S2 4*, and an ascension material chest every 10 draws.
But whether that makes it a better deal for you depends greatly on what you have and what you really need.
For me it comes down to what hero do I want/need. The heroes in Wonderland and the February HOTM offered me on the Queen. Not enough when I see Atlantis will offer (probably) two new heroes plus two past HOTM and the new HOTM.
OTOH, if the event was Avalon or the sand guys were up, then I would have skipped Atlantis.
And, like @garanwyn points out, the chests with AM are a big point in Atlantis’ favor.