Questions about Grinding in Summer

There are two things I need to ask from this wonderful community :

1. Should I grind Event CE (summertime mistress) or complete all chapter first? Right now I am in Chapter 7 building ranch with no event CE other than the lumber event CE from FP Gacha and one stone CE. I wonder am I being ineffective?

2. I am lacking in strong Iron servants. I need help from you guys, especially if you have Arjuna, Tesla, or Lancer Altria at Max Lv along with Pirates Party equipped on them. If you guys have it, please let me add you guys as a friend in-game, I promise I will use your servant A LOT in this event. 😁