Since this is a Trinity deck, the Banlist is completely different to what we're used to: We can use some TCG/OCG banned cards, since the nature of the format makes these cards a lot more fair than in the Konami handled formats. Examples of such cards are El Shaddoll Construct, Premature Buiral or Blackwing - Godu the Vague Shadow.
The deck's main focus is to put enough pressure on the board to have your opponent commit to their Extra Deck, making Shaddoll Fusion's strongest effect (Fusion Summoning from the Deck) live. To get to this point, you need 2 things: cards that put pressure on your opponent and ways to get to your Shaddoll Fusion faster.
To put pressure on your opponent, Subterror monsters are very adequate, since they're big, they're easy to summon, and they have powerful effects. The most common way of summoning your Subterrors is throught Subterror Nemesis Archer and Subterror Nemesis Warrior, so that's the reason why I'm using a Trinity on a 2nd copy of The Hidden City: It not only searches our Subterror Nemesis monsters, but it also helps triggering our Subterror Behemoth Monsters and its also has a pretty decent battle protection effect.
Since July 2018's list, Shaddoll Fusion has been co-limited, so that means that only 1 copy of the card can can be used, decreasing the deck's consistency. In order to circumvent this, and get to Shaddoll Fusion as soon as posible, I decided to use 2 trinities (yes, 10 more cards) to play another 2 copies of Shaddoll Hedgehog. This aslo helps with the late game, since having more Shaddoll monsters on the deck means you can resolve Shaddoll Fusion more times throught the duel.
The second co-limited card I choosed to play was terraforming, since it pairs well in a deck with so much Field Spells, and helped with the consistency of the LIGHT engine chosen to run in the deck. The A-B-C Union monsters: a flexible engine that is good both making Rank 4s and Links, while having a very powerful boss monster that is quite easy to summon.
That, paired with a lot of generic good cards and some FLIP support cards, is my approach on a deck that is currently considered one of the top decks of the format.
If you are interested on the format, you can read an introduction to the format here!