Atlantis - Alasie, Talrak, Mitsuko, Margaret - all decent heroes except Margie, especially Alasie, but I personally plan to skip it. There’s so many blue snipers everyone should have one already, doesn’t have to be the best in the game. Talrak can be skipped - Miki comes back later this year.
Springvale - skip completely, even if you hoarded EHT. Heroes here are terrible, even the new ones. Better wait with tokens till summer and hope for decent fire HotM
Wonderland - chance at rabbit, I plan to limit myself to coins and a 10x pull. It’s a decent event, but it will come back, and beside rabbit it does not bring any top tier heroes.
Costume - option to consider especially if the new costumes make it into the game. But I wouldn’t overdo it, perhaps a 10 pull. It will come back monthly anyways.
Vahalla - this is where I would summon the most if I could. I hope for Alfrike featured, and I wouldn’t want to skip the month completely as I need strong yellow option and Malosi would be welcome to my roster.
But as others said, with Gravemaker coming back in May to Atlantis, that is where I plan to spend most of the gems. It would be sad to skip Malosi, but GM + Clarissa just too strong.