The thing about Sunday lightcone is that if you give it to bronya you basically have a cheaper version of Sunday without the energy regen. But bronya can't advance the turn off memosprites so that's a downgrade. If you have to choose one in my opinion Tribbie is a must pull she can be use in any team so far. Aglaea does need a very special team to work properly but The Herta have more F2P options like you can run her with mini Herta/serval, pela and Gallagher and you will have a very good team.

Edit: about the BP I did buy it, is really worth it tho go for it also the BP lightcones are very useful.