Hi, I'm AquaHulcusTacos, and this is my 3 Colour Deck

[4] Aqua Guard
[4] Emeral
[4] Crow Winger
[2] Essence Elf
[4] Rikabu, the Dismantler
[4] Aqua Hulcus
[2] Crystal Paladin
[2] Avalanche Giant
[26]

[4] Dimension Gate
[4] Brain Serum
[4] Tornado Flame
[4] Searing Wave
[16]

I own only [2] Essence Elfs. And I won't add Terror Pits, since I don't own any, plus I like Tornado Flames. I don't have any Crystal Lancers, and I prefer Crystal Paladins over Lancers.

Should I drop the Brain Serums for 4 Crystal Memorys? And maybe add Coriles or Locomotivers?

drop the essence elf for elf-x.

if u were to drop the serums for anything at least make it energy streams and definitly add coriles. I'm not sure, but i dont think it is a good idea to splash in locomotiver, but do what u like