Thank you all for your answers, they were pretty informative indeed. :3
To be honest, I'm still getting used to play Aigis, so I'm likely to be confused easily here. >_<

Seems very reasonable to wait until I really want a certain unit, before spending my SC, thus avoiding possible regrets in the future. I have to admit that I'm not particularly interested in any of the current spotlight units (Maybe Olive, but not quite much), so I think I'll wait calmly, while keep improving my current team.
So far the only girl I'm desperately struggling to get is Erika from LoV, so I guess I don't need to rush things here at Aigis.

But it's true that Monica's DC boosting feature is something interesting to consider, though I think I'll pass this time.

Regarding my team composition, well, I still have a lot of work to do before getting a good team, and considering what I have been reading here and there, looks like I'm taking a bit more time than the average to develop a good team.
Keeping that in mind...

- 50CC50 Soma and 50CC40 Daniela for physical rear.
- 50CC23 Calliope and 43lvl Cloris for magical rear.
- 50lvl Valerie for AoE rear, plus another one I need to level up yet.
- 50CC32 Katie and 27lvl Phyllis as soldiers, plus a bronze soldier for anti-rush purposes.
- 50CC39 Leeanne as tank (I don't have another decent tank, lol).
- 50CC28 Kerry as duelist, plus an Elaine I haven't started to level up.
- 50CC18 Alissa and 25lvl Dorca as healers (I know, I have to work on Dorca asap).
- I haven't started to level up Cecily and Cypria, to be honest, but they're there.

Further comments and suggestions would be appreciated.