Getting the dice you want:

To get the certain monsters you want (such as Holy Doll or Kuriboh), all keep selecting ‘New Game’ at the title screen. Every time you start a new game, you get randomized dice. If you are unhappy with what you got, do it again until you get the desired combination of monsters.

Good Matchups

Certain types work better against others. Here’s a quick list of what’s effective:

Beast is most effective against Warrior
Dragon is most effective against Spellcaster
Spellcaster is most effective against Zombie
Warrior is most effective against Dragon
Zombie is most effective against Beast

Symbolic Meaning

Symbols that appear over a monster’s level have meaning:

Feather – indicates that the monsters can fly and can only be attacked by other flying monsters. It can fly over other monsters, but monsters can also move under it. Flying monsters cost double in movement costs.
Tunnel/Cave – indicates a monster that moves underground to move around. It can also move past other monsters.

Crocozaurus

Defeat Joey in free duel.

Exploding Disc

Defeat Mokuba.

Orgoth The Relentless

Defeat Joey. Alternately, defeat Duke Devlin sixteen times in free duel.

Red Eyes Black Dragon

Defeat Joey in the world championship.

Red Eyes Black Metal Dragon

Defeat Joey in free duel.

Summon Crest

If you need a Summon Crest, hold B to roll at least one. Note: This does not work on level 4 dice.

Warp Hole

Defeat Maxamillion Pegasus.

Good dice

Defeat Marik or Odion in free duels to get very good dice, such as Gemini Elf, Orgoth,and Metal Zoa.

Play the Paradox brothers a few times to get level 4 dice.

There are three tournaments in the game (Normal, Reverse and Dark). Win the championship in all three to unlock all except two of the dice in grandpa’s store.

Easy wins

Save you strongest monsters such as Harpie Lady Sisters or Mystic Horseman by playing level 1 monsters to make a dungeon path. Then when your dungeon path is close to your opponent, try to summon your strongest monster. Have lots of movement, defense, and attack crests.

Defeating Marik

Try for your level one monsters first. He usually goes first for Blue Eyes Ultimate, Black Skull Dragon, or a level 4 Treasure Chest which destroys every monster in the dungeon.