PRIMER
The Commander:
Glarb's most useful feature is his ability to play lands and 4+ mana spells from the top of your deck while being able to look at the top card of your deck at anytime, and his secondary feature is to Surveil 2 (look at the top 2 cards of your library, and put any number of them back on top in any order, or put any number of them into the graveyard). Many of the most useful cards in the deck interact with these abilities (see the Card Finders, Graveyard Recursion, Put This In The Graveyard, and Top Deck categories). Glarb has low power, and he has to tap to use his Surveil ability, so you're probably not going to want to attack with him. But he has decent toughness, and he has Deathtouch (kills anything he damages), so he's a fairly useful blocker.
Big Frogs:
Yargle and Multani is the big damage dealer. He's the best card to have on the board for Season of Gathering, and if you can manage to attack on the same turn with Twenty-Toed Toad after that resolves, you win the game. He's somewhat ineffective on his own, but he smashes opponents if you have Brawn, Filth, or Wonder in your graveyard (see Put This In The Graveyard).
Board Wipes:
Damnation simply destroys all creatures. Cyclonic Rift can be used as spot removal in a pinch, but it's far more useful as an asymmetrical board wipe. Season of Weaving can draw you a couple cards in addition to wiping, and it has an alternate use of cloning creatures or artifacts (bear in mind that clones of Legendary permanents die immediately after entering). If nothing else, you can simply draw five cards with it.
Card Draw:
Season of Gathering is great card draw if you have a high-power creature, and it can also buff your creatures or wipe all artifacts and/or enchantments. The Delve ability of Dig Through Time and Treasure Cruise can make use of otherwise unusable cards in your graveyard by exiling them to reduce the neutral mana cost.
Card Finders:
Buried Alive is mostly looking for the three creatures in the Put This In The Graveyard category, but you could find a different creature to use any of your creature-focused Graveyard Recursion cards on. Demonic Tutor puts anything you want into your hand. The other cards put things on top of your deck, so they're most useful when your commander is out in order to cast whatever you put on top.
Defense:
If you have an abundance of lands, and especially if any of your land-focused Graveyard Recursion cards are on the board, Constant Mists can shut down combat for as long as you need. Lightning Greaves and Swiftfoot Boots give a creature haste, or the ability to attack and use tap abilities immediately, but their main purpose is to make it harder to get rid of your most useful creature on the board.
Graveyard Recursion:
Animate Dead, Necromancy, and Reanimate specifically target creatures. Note that they can also target creatures in other people's graveyards. Crucible of Worlds, Conduit of Worlds, Ramunap Excavator, and Walk-In Closet let you play lands straight from the yard and synergize particularly well with the lands in the Put This In The Graveyard category. Hedge Shredder synergizes directly with any lands that get Surveiled by Glarb, and Muldrotha is a recursion powerhouse on a big 6/6 body.
Lands Matter:
Many of these cards have some sort of effect that triggers whenever one of your lands enters the battlefield, and they synergize with most cards in Mana Ramp and the lands in Put This In The Graveyard. Note that The Gitrog Monster cares about lands hitting the graveyard and forces you to sacrifice lands at the beginning of your turn, but it also let's you play an additional land on each turn. Avenger of Zendikar is a potential game-winner if you have a lot of lands on the board and can put one or two more on the field after it lands. It's also the perfect creature to target with Season of Weaving, Springheart Nantuko, and Lilysplash Mentor.
Mana Ramp:
Dryad and Exploration allow you to play additional lands per turn. For the sorcery cards in this category, note the land-type that each card can find. If a card cares about finding a Forest, that card can also be a Swamp or an Island. Farseek says the land enters the battlefield tapped, so you'll probably want to prioritize looking for a land that already enters tapped, such as the lands in the Top Deck category.
Put This In The Graveyard:
The creatures in this category are meant to go straight to the graveyard with Surveil or Buried Alive- only cast these in a pinch. They make it easier for your creatures to attack without being blocked, deal damage in spite of being blocked, and block flying attackers. The lands are useful to play from the hand or from the top of the deck, but they're the best lands to play from the graveyard using the Graveyard Recursion land-focused cards, since they can be replayed over and over again. This is especially great for triggering Landfall abilities for several of the Lands Matter cards. Note that some of these lands can only look for basic lands, while the others care specifically about whether the land is a Forest, Island, or Swamp. Again, a Forest can also be an Island, etc.
Spot Removal:
Sometimes you just gotta get rid of someone else's shit.
Top Deck:
These cards are great on their own and even better when your commander is out to cast cards from the top of your library. The lands all have their own Surveil ability, and Enhanced Surveillance let's you Surveil 2 more cards whenever you do so. Brainstorm is great for when you want to put something in your hand on top of your library (like a creature from the Put This In The Graveyard category). Sylvan Library lets you filter cards on your draw step, but you'll benefit more from paying the life to keep the cards in the early game.
Utility Frogs:
All of these cards have fairly unique mechanics. That said, many of them have situational synergy with each other as well as other cards in the deck. A few have Reach, or the ability to block flying attackers. Using Lilysplash Mentor on Avenger of Zendikar can build a sizeable army of plant creatures. Twenty-Toed Toad can win the game by targeting Yargle and Multani with Season of Gathering.
Utility Lands:
Bojuka Bog nukes someone's graveyard. Urborg fixes your black mana, but it's mostly in the deck to synergize with Filth (see Put This In The Graveyard).
