I'd say perhaps try the summons now. Currently before the event, Monica and Marius have bigger chances of getting summoned and the units coming the next event while good, aren't really the best units you can get (samurais have a place but a lot of other units can be much more important to get).
Monica if you can get her will boost all your demon crystal drops by 3% as long as she is on the team so having a higher chance of getting her is quite nifty.

That said, while Monica is a good DC booster and Marius is the currently best mage (though he is a bishop), we do get a nice mage the next event so you might even want to wait and see what the events in the future bring.

As Kotono said, check the spotlight units and wait for something you really like and spend at that time. Nothing wrong with that.