It can be difficult to know which card to counter, but I generally ask myself, Based on the information given, what card is the bridge to their end-game?, and counter that spell
If youre willing to wait until your fifth turn to have found the needed legendary creatures and are happy with a 75% chance of having Kolvori be a 6/6, then you only need a mere thirteen non-Kolvori legendary creatures, which is a much easier number to come to and still sounds acceptable to me
Lands Thirty-nine lands is a lot for Commander, but I generally like running high on my land counts anyway so Im a big fan of this
You can also exchange Crystals for additional coins in the shop, though Crystals are much harder to collect so you might want to avoid doing this
Remember Abzan Company
Muldrotha, the Gravetide decks more than justify their existence with incredible card advantage