1. Your team is nowhere good enough to be able to take on most event missions at the moment, and i recommend just focusing everything on leveling and affection items through challenge missions.

2. You will want Katie, an archer, and Iris up first. Since you seem to lack extra archers (do NOT use silvers as fodder, it is trap) i would recommend going for Daniela. So Katie, Daniela and Iris, get them to 50 and then CC them.

3. You have a really good set of units already, so don't aim for more summons at the moment. If you want to be able to do the event missions near the end of the event i would recommend spending some on charisma or stamina refills in order to make your units better.

4. You really only want mostly silvers or better. Bronze units CAN be useful, like 2x bronze soldiers to have as mincosted units for special missions, or a bronze heavy armour or mage for certain things. But in general, discard the irons, just sell them or use them as fodder.

5. Yes it was a bad idea. Your Alissa lost 20 levels worth of stats. In general you only want to CC a unit at 30 if you are going to feed said unit to another. Always aim for 50 for units you want to use, otherwise you lose stats.

Edit:
I recommend looking at the stickies on this forum or in the link below for some good beginner tips:
http://millenniumwaraigis.wikia.com/wiki/Beginner_Guide