I've been playing Primal Surge Muldrotha, and it's really fun (strong too, even against fine-tuned decks). Once your opponents know you have Primal Surge, it becomes a fun game of threatening doom. Some suggestions:

Lands: [[Bojuka Bog]], [[High Market]], [[Ghost Market]], [[Tectonic Edge]], [[Strip Mine]] (you need land destruction)

Planeswalkers: [[Kiora, the Crashing Wave]]

Artifacts: [[Skullclamp]], [[Perpetual Timepiece]], [[Baleful Strix]], [[Solemn Simulacrum]], [[Ashnod's Altar]], [[Altar of Dementia]]

Creatures: [[Clever Impersonator]], [[Sidisi, Brood Tyrant]], [[Hermit Druid]], [[Golgari Grave-Troll]], [[Shriekmaw]], [[Kokusho, the Evening Star]]

Enchantments: [[Journey to Eternity]], [[Elephant Grass]], [[Bear Umbra]] (amazing on Muldrotha), [[Mind Harness]], [[Carpet of Flowers]] (these last two are my favourite cards in the deck)

The deck is quite tool-boxy, so having tutors really increases the consistency and power level: [[Defense of Heart]], [[Fauna Shaman]], [[Birthing Pod]], [[Protean Hulk]], [[Pattern of Rebirth]]. But these are more expensive, of course. Only the last two are under $10.