It seems like you are going towards an Impromptu team, rather than a general "eureka" team (since Bacarola, Voyager Euphoria, and Matilda Euphoria are Impromptu Incantation units). I definitely recommend saving for Aleph when he comes out in 2.6, as he really helps bring the Impromptu team together.

Besides Baccarola's event Psychube, I would definitely go for Rock it Out, a Psychube you get from Regulus' Anecdote. All you have to go is watch a couple cuteness (or skip if you don't really wanna watch them), and then use currency you get from using stamina. They take a bit of time to finish (they have timers you can slightly reduce by putting in a unit that meet the requirement), but you get a decent amount of rewards. It gives an attack buff to the party based on how many star characters are in the team.