Theres no real counters theme in the base build of the deck, and youd have to do a lot of work to turn the Dryad Druid into some kind of combo engine
1-Mana Cantrips Renegade Tactics Ancestral Anger Warlord's Fury Rile Telim'Tor's Edict Crash Through Crimson Wisps Expedite Overmaster Might of the Meek Impolite Entrance You can run these for their main effects, but theyre generally slightly sadder versions of Opt and Consider for spellslinger and storm decks
Theyve got no problem keeping sufficient devotion on the field, and Ive seen Karametra decks routinely dig every last land out of their deck and onto the battlefield
Lightning Greaves, too, can never be reprinted enough and will protect your expensive horrors while allowing you to swing with them immediately
I've seen some people asking for Snapcaster Mage and fetch lands in Commander decks, but that's not practical, and lacking super-high-end cards isn't the problem with Commander 2018