The Ritual exam is pretty hard at first. You need to be able to summon 5 ritual monsters to get the 300 score, so to do this, you must be able to make the game last a while. The deck I've come up with is pretty good, to the extent that I can win versus characters outside of the exam. (This deck changes according to the ban list. I would usually have Black Luster Soldier - Envoy of the Beginning in the deck but it is currently banned in the time I am currently at in-game.)
Monsters: 21 3 Paladin of White Dragon 2 Relinquished 3 Manju of the Ten Thousand Hands 1 Sonic Bird 2 Des Feral Imp 1 Sangan 1 Kuriboh 2 Magician of Faith 1 Witch of the Black Forest (I usually add a Senju of the Ten Thousand Hands if this is banned) 1 Marshmallon 2 Chaos Sorcerer 2 Blue-Eyes White Dragon
Spells: 14 3 White Dragon Ritual 2 Black Illusion RItual 1 Swords of Revealing Light 1 Harpie's Feather Duster 1 Scapegoat 1 Monster Reborn 1 Change of Heart 1 Confiscation 1 Mystical Space Typoon 1 Reload 1 Burst Stream of Destruction (This game has a bug that allows this card to be used without Blue-Eyes White Dragon. it is just like Raigeki)
Traps: 5 1 Mirror Force 1 Call of the Haunted 1 Ring of Destruction 1 Torrential Tribute 1 Threatening Roar
Paladin and Relinquished are some of the easiest ritual monsters to summon. I use 3 Paladin and only 2 Relinquished because, believe or not, sometimes the opponent does not have a monster worth taking. Paladin can consistently dominate the field when summoned, and can at least summon Blue-Eyes as a 3000 ATK monster that will destroy virtually anything by battle. Since Paladin is LIGHT and Relinquished is DARK, I figured I could have a chaos element in this deck so that I could use Chaos Sorcerer. I realize that Chaos Emperor Dragon could fit in the deck and win games by itself, but I felt that it would dominate the field and stray away from the theme too much. Sorcerer will always be helpful no matter the time it is summoned. Manju and Sonic Bird are necessary so that your ritual summoning is that much more consistent. Des Feral Imp is a card with decent stats by itself, plus it allows me to put back whatever card I have in the graveyard to my deck. It could be a ritual card that I could search for with Manju, Blue-Eyes to use with Paladin, and any other card I may just want to be able to draw/search for again. Kuriboh may seem a bit awkward, but it can fulfill the tributes for Relinquished, be a dump in the grave for Chaos Sorcerer, and last but not least, protect me. Reload is pretty necessary as having poor hands is natural with running so many Ritual cards.