The earliest that you can activate Sundial of the Infinite's ability is during your upkeep step, after abilities that trigger "at the beginning of your upkeep" have been put onto the stack but before they resolve
Thinking about the potential here may be a tad optimistic, but it gets my Timmy heart pounding
At the top end, Volcanic Island proves that Izzet is king, at least as far as collectors go
Consider adding cheap staple cards like Kodama's Reach, Cultivate, or something like Emergent Sequence, Greenseeker (it also discards you a creature that you can pick up with meren at the end of turn), Primal Growth (good sac outlet too), Dawntreader Elk, Deathsprout, Diligent Farmhand, Rampant Growth, and notable Yavimaya Elder
Beyond that, green also offers you ways to add extra lands to the board, even at instant speed
Have you ever seen a real playtest card up close