Half shut, spell of absorbing light, and stray lambs work great for gandora. Once gandora is put into attack position you can summon stray lambs and activate the effect to destroy two cards for the price of one.
I believe gandora does best in the late game. What the strategy to this deck is to weaken your opponent to ideally between 1500-2500 LP and filling up your field and the opponents field in the process. You can do this by using the supporting cards of relinquished and twin headed thunder dragons. Also, it's great for stalling to have your opponent have even more cards in his field than you with "Windstorm of Equata" and "Sphere Kuriboh". Late game gandora is where the card shines since having "Desert Sunlight" is very pointless, and the point is to have Gandora to finish your opponent, use castle wall, blockman and shattered axe to stall. Do the damage with "Twin Headed Thunder Dragon" and "Relinquished" and you could even use "Sonic Bird" with Kaiba's "Peak Performance" skill. Once he's in kill range (1500-2500 LP) summon gandora, use his effect, and win the game.
Footnote: Overwhelm could be used in the deck if your opponent chooses to negate your attack with "Sphere Kuriboh".
You can use desert sunlight to flip him feom being set to face up defense position which wouldnt make him vulnerable to being destroyed at the end of the turn because he technically wasnt summoned nor flip summoned. Could also use cost down so he would be a one teibute monster and allow there to be one more monster on the flield so you could gain another 300 atk when you use his effect.
Toy Magician only trigger its special summon from opponent's card effect.