This Deck is designed to go first, you could go second but if you're against a Thunder Dragon deck you will have troubles or another kind of Control Based Deck.
Although at first you could think that the Mythical Beast Engine will conflict with the Endymion there is no such thing because you can use Magical Citadel or Mythical Institution to gather Spell Counters to activate all the effects do you need.
The Extra Deck doesn't have much problem to understand.
The Side Deck is designed when you go second.