I've started to get into breeding max stat sylesti and was wondering about mana. How do you increase the base mana?

Unfortunately, at this time you can only increase base mana if you introduce a sylesti that has highter base mana.

Currently, the only way to get 120 in non-fabled species is to find a four-star one in the wild and catch it (which means all the other stats would be... common base junk.)
Puffadores are an exception because they obviously aren't found wild. They can only get up to 110 base mana (there are only two of these amongst all the Tamed puffadore in Sylestia) (I expect they're some hecks of expensive in the puff shop. I think there's also one 105 mana puff)
(Exclusive non-fableds, including puffadore, only have 100)

Exclusive fabled pets have 120, easy enough.

One exception to 120 mana, it IS possible to get 130 mana if it's a ny'vene from the shop (again, I expect that the ones that ARE are ludicrously expensive)


I believe Krin has implied that there will be common-species wilds with higher base mana in the MegaZone (he definitely caught this aurleon while he was testing the MZ at one point and posted her during some discussion or another about it)
(who knows, maybe someday we'll get philters specifically for HP and Mana)

thank you, that's really helpful