So I've got my only 6* maxed with ampys, is there a generally strong 5* that would be the go-to in terms of buffing up?

My initial thought is Dipladenia, since her abilities are rather useful.

Interested to see what others think though.

Strong 5* with Bloomed Forms and good Abilities:

Oncidium, Evening Primrose, Lantana, Camellia, Justicia, Toad Lily, Edelweiss, Leucocoryne, Lavender, Chocolate Cosmos etc.

There are also some strong 5* without Bloomed Forms:

Cymbidium, Dahlia, Cyrtanthus, Peach etc.

Dipladenia isn't a bad choice either cause she also has a Bloomed Form and like you said: Her Ability is usefull and a rare Ability as well.

That's a lot of ampys I really haven't had the time to get near maxing even 1 girl....it's something crazy like 100 of each isn't it

You could divide them between some girls. For example, a girl with Counter Attack or a passive defense buff would probably benefit more from a DEF ampy than any other girl, while girls with an ATK+ passive will get more milage from ATK ampies.
Another thing to consider is, that ampies do give some experience. At higher levels, it doesn't add much, but below lvl 40 the increments are still fairly noticable.
Not sure where to feed the Health ampies, there aren't any passives doing anything percentile based with health, so I'd feed those to the waifu.

This is the first time I'm hearing of this bloomed form, is that the evolved form that maxes at level 70? or is there some additional thing eventually coming?

Bloomed form is a second level of evolving on top of the evolving to lvl 70 we already have, which isn't even implemented in our version of the game yet. Expecting it within half a year is probably a bit optimistic.