Thunder (SPIRIT CALLER 2006)

In Yu-Gi-Oh! GX SPIRIT CALLER you collect multiple duel spirits that give your character passive buffs; to level up the spirits, their card has to be face-up on the field to gain experience when you win, nothing else.

I'm not going to lie, this is a terrible deck. First thing to note, this is every Thunder-type monster in the game; one advantage is "when you win" you'll get the [Limited ATTRIBUTE] & [Limited Type] experience bonus, leading to faster levelling up. Try to stall until you can summon Sanga of the Thunder, use Batteryman D as a wall to protect your field, use trap cards to destroy enemy monsters. If you can special summon Batteryman D, and combo with Aqua Chorus you'd get a wall that would stall most of the opponents. If you tribute summon Zaborg his effect is mandatory, so play Cost Down if you want an easy summon. Just use this to grind no-named duelists, until your Batterymen, or Wattkid (Oscillo Hero #2) reach max level.

Side Deck: If you acquired Harpie's Feather Duster (from Blair)/Monster Reborn (from Atticus), replace Heavy Storm, or Premature Burial. If you haven't unlocked Wattkid/Batteryman C, fill your deck with Solar Ray/Elf's Light. I use Umi field spell since it would depower Machine-types, no one in the game plays Pyro-types.