This is a very janky deck with a fun win condition: draw through your deck and win with Thassa's Oracle. This means that you don't have to choose between card advantage and win condition, you get to do both at once. And because we are doing this with Risen Reef, you also might be gaining tempo (in the form of ramp).

Fog

This is a fog deck, using Pause for Reflection to largely ignore our opponent's creatures. To deal with non-creature threats, we have four Negate.

Going Off

This deck wins by having lots of reef triggers. This will allow you to draw through to more elementals which can trigger reef, which will allow you to ramp more, draw more, win more. To protect our combo, we have 4x Negate and also Teferi's Time Twist (which, in addition to protecting against spot removal and sweepers, can also be used just to get an additional ETB trigger from a permanent).

Finale of Devastation helps you tutor out your reefs or other utility cards perfect for the moment; Quasiduplicate will duplicate your reefs or other elementals with fun ETB triggers; Yarok, the Desecrated can start multiplying your ETB triggers.

Guild Summit is the real galaxy brain card of the deck. This turns many of your lands into additional card draw (which might be put directly onto the field by Risen Reef anyway). Playing in gates also helps keep this deck budget friendly (because, let's face it - this deck isn't competitive enough to blow your money on).

Elvish Reclaimer helps you tutor out a land you need for its ETB trigger, either a gate for card draw when you have Guild Summit, or a Temple of Mystery to scry, or a Plaza of Harmony to gain life. We like to hold up 2 mana on our opponent's turn anyway for Negate, Teferi's Time Twist, or Anticipate, so this is a good alternative 2 mana dump.

Oops, No Fog

Since Thrones of Eldraine there are now some crazy good, popular, main board cards which nullify fog: Bonecrusher Giant and Questing Beast. This is a jank deck just for the fun of it - meant more for Friday Night Magic than for tournaments.

Budget Friendly

This deck is very budget-friendly and utilizes a lot of commons and uncommon cards you may own anyway. It's easy to sub out the more expensive cards with alternatives you own. If you don't have a Yarok, the Desecrated, sub it out with Thassa, Deep-Dwelling if you already own one, or sub it with nothing at all (you don't reall need this card to win). If you don't have Finale of Devastation maybe consider some Neoform to tutor out your reefs off of a Thassa's Oracle or a Leafkin Druid (probably a better card to play anyway if you don't have a Thassa or a Yarok on the top end). You could easily make a version of this list that was under $40, or even better - a list that utilizies cards you already own.

Feedback about how to improve the list is always appreciated :)

If you play with it, let me know how it does