The deck is an ongoing brew. There are plenty of cards to consider, as well as tweaking card counts. Some cards and reasons for possibly including/not including them are below:
Ash Barrens: Sometimes better than Evolving Wilds, sometimes not. I went with the 3/3 split on wilds/expanse because of the double landfall triggers they give, and ability to get landfall triggers at instant speed. Ash barrens also feel really bad to flip with Explorer's Scope, whereas an Evolving Wilds lets you get an extra landfall trigger on the following turn.
Expedition Map: Could be a 1 of inclusion, as it's tutorable with Trinket Mage, fits the theme, and grabs a non-basic. If I ran this, I'd probably add in some utility lands. As is, doesn't seem particularly good.
Groundswell: Instant speed combat trick that essentially acts as an extra two triggers of Adventuring Gear. If I wanted to lean in more on the aggro aspect of the deck, it could be a solid choice, but with the more mid-range plan I don't think it works out. Would also require more green mana.
Khalni Heart Expedition: Obviously there's 3 in the mainboard already. I've tested with 2, 3, and 4, and 3 seems to be the sweet spot. If a card underperforms, I may cut it for a fourth. With all the brainstorms, hawks, fetch-lands, and trinket mages though, the deck gets thinned enough for 3 to be reasonable.
Kodama's Reach: for 2 guaranteed landfall triggers, sometimes on the same turn, is decent. I'll be testing this deck with a few, although once again I would have to lean more in on green. Could probably throw in 2 green gainlands.
Ornithopter/Flayer Husk/Myr Servitor: I've tested with these as a tutorable creature with Trinket Mage. All were okay, with Myr Servitor as the worst performing as it requires 4 of to be useful. 1 of Ornithopter or Flayer Husk could still be ok, but I rarely find myself needing creatures from my mages. Could be a sideboard option though.
Executioner's Capsule: Tutorable removal with Trinket Mage, but would require running black mana. Will be testing with some to see how it does. The biggest problem is if we're using mage to tutor for the capsule, we can't also tutor for the black land, requiring us to search for it with fetchlands. Could be an okay idea, but we already have enough removal through Journey to Nowhere and Sunlance.
Blazing Torch: Tutorable shock for 2 that sometimes gives us evasion. Seems like a better option that
Leonin Squire: Adding capsules into the artifact package would make this useful. As is, it only helps protect against counter spells and artifact removal, and recurring Dispeller's Capsule from the sideboard. Could be sideboard tech.
Crop Rotation: Fixes our colors and gives us a landfall trigger. Could be an okay 1 or 2 of.
Khalni Garden: On color and on theme. Would be decent if we leaned in more on utility lands with Expedition Map and Crop Rotation, or if we went heavier on green. As is, we can't tutor it so the Forest and Tree of Tales seem better. The 0/1 holds equipment well, and in the worst case scenario is a chump blocker.
