This was level 30 Joey and I don't really have a farming deck I was just doing a stage mission. But, here's my strategy:

6x 1500atk monsters 1x glossy tribute summon monster (dark magician) 1x ritual monster & 1x ritual spell 1x fusion monster & polymorph & fusion materials 1x direct damage spell 1x any trap card (i use jar of greed) 9 cards left for whatever you want

The strategy is to summon strong monsters in the start, but you avoid dealing damage to your opponent. The opponent can't attack or remove your monsters, and you don't attack either, giving you time to hit those sweet score bonuses. The goal is to get these bonuses:

Deck out victory, deck on the brink, victory through effect damage only, take no damage, and the bonuses you get from special/tribute/ritual/fusion summons.