Summer Tiki help

If she's used in flier emblem, the -atk will be patched up with a hone/goad buff. Ignis and qr is good. If you have extra copies of dc lying around then go for it. Otherwise her atk/def bond is good.

Defninitely could work as a good archer counter on a flier team with DC and Iote's Shield. QR is probably best without any speed boosting skills to help her double.

The atk bane isn't really going to hurt when flier buffs are in play. You do want to buff her atk, though, because she prefers to one-shot enemy dragons (and she will often succeed, in part because most of them focus on def more than res). Doubling to beat them is fine unless it's an enemy Tiki-breath, but she will get significantly hurt in the process and it's unnecessary. +def is good for trying to survive one hit from a Falchion because she doesn't have reams of HP like Nowi/Fae, and it's also just good generally - swords, axes, daggers, archers if you use Iote's shield, some lances

Whether you should invest in her is a question of your play style and what teammates you have available to choose for her. DC + ignis is very explosive but I don't recommend it without Iote's shield because her res isn't amazing; aether can be tried for sustain but her low HP will tend to be a problem (great candidate for summoner support).

QR is extremely solid because she's in the range where minimal investment enables her to block doubles from super-fast units (who are, understandably, extremely hard to double naturally). If she wants to give away spd buffs to her teammates so that they do the attacking, this is a good option. Chill spd is the aggressive option and excellent on arena def to mess with people because it's unblockable and not subject to AI mishandling; give her speed buffs adding up to +8 or +10 and she'll probably double most units naturally. I think I prefer chill spd on a +spd flying Tiki, but even at neutral it's fine, especially if Camilla's Axe is involved.