If you have the gear which gives 1 might when you attack or defend alone. And you have a sprite at base and a unit which creates a sprite in the location it moves from. Let's say you have that unit defending. Reveal a tide turner to move it to base and move the sprite to the battlefield. But that also means a new sprite is added when it is moved, does one soirtr get the solo attack buff before the second sprite is generated by the move?

Yes — the unit that arrives at the battlefield gets the +1 from Mask of Foresight.

The arriving unit gains the Defender designation the moment it enters (while the original defender has already left), and at that instant it is the only friendly unit there — so the "defends alone" condition is met and the Mask trigger goes on the chain and is locked in. The second Sprite isn't created until the moved unit's "when I move" trigger resolves later on the chain, so it arrives too late to cancel the buff (and it can't trigger Mask itself, since it enters while another unit is present). Per FAQ 10067, once Mask's trigger is placed on the chain it resolves regardless of units joining afterward.

One correction to the play: Tideturner's effect moves Tideturner to the battlefield and the chosen unit to base — so the unit getting the buff is Tideturner, not the Sprite sitting at base. (Rule 383.4.f; FAQ 10067)