Originally Posted by Drip

The idea I had, was to stack on their main feature.
-Fritillaria gets a percentile ATK bonus upto 30% whenever a unit in her squad makes a special attack. The higher her ATK, the bigger the bonus. So raising her ATK by 100 points actually raises it by 130 points. More ATK value from my ampies.
-Alpinia's has life leech, which is a percentage of the damage she deals on her special attacks. That means her ATK acts both offensively and defensively. More ATK means more health recovered.
-Anemone and Helenium are counter-girls (like your Apricot). Whenever they take damage, they deal damage back with their DEF added to their ATK. So, their DEF acts both Defensively and Offensively. More ATK or HP always helps, but these girls are the ones who benefit more from DEF than other girls, so it was a no-brainer to give them my DEF-ampies.

Right now I'm working on Acacia, who is a bit of a special case. Her main feature is the ATK debuff on enemies. Stacking this debuff in a squad and combining it with high DEF can reduce the damage dealt by some higher lvl raidbosses (Like the Galaxyfly in this event) considerably. It's a bit too much to expect that damage to get reduced to 1 point (the minimum), but reducing a hit worth several thousand points of damage to just about 300 points definitely helps her survive longer. And because she got so many rounds to deal damage, I figured I'd boost her ATK as well. Well, and she's waifu, so uhhhhm, yeah

Also keep in mind that the future Promotion Traits we can assign to individual girls has one called "Healing Boost" that allows a girl to buff her health up to 125% of her normal health, so in Alpinia's case, health ampies will give her a larger base and defense ampies will help her keep it.

For me, I've fully amped only three so far: Dendrobium, Saffron and Alpinia, though I will admit that amping Saffron's attack seems indulgent. I just got OCD about it.

I actually go the other way about ampy's. The girl (6*s only right now) with the least in a stat gets the ampy's to buff her up. Hanamomo for instance has full +400 def because without it she only has 1600 >.>