Great theme deck to get a younger kid into Magic! Mayael is definitely more logical, but I think you're right they'll switch our Gishath after a bit. Seeing as the deck has some serious money it, I don't feel to afraid to suggest Cavern of Souls as a land to slot in, if you're gonna invest all that mana in a big dino, you want it to land, and if he switches the commander out, then he has a guaranteed commander out too. I also might suggest Burgeoning as a ramp piece because your curve is high, and that enchantment can allow you to ramp really quickly in multiplayer games. Otherwise, I agree with most the other suggestions, namely Rings and Citanul Flute. Deck looks great man!

Thanks for the comment, untraceablez. The budget here is a bit misleading...most of the dual lands are cards I've had for a long time, and the Gaea's Cradle....well, I was playing pretty heavily during the Urza block, so I got some in packs. That said, Cavern of Souls is an unlikely acquire. Burgeoning is a good suggestion, too. I'll have to see if I can make a spot for Citanul Flute.