This is my POV you can use it as brief.

- For current event you need at least 2 strong group to tackle enemy.
90k+ strength per group will be my suggest.
And you have to place one high speed (600+ speed) at the bottom start to full clear map.

- Re-issue and perma-event is something you should do if you can spare time and stamina.
But first priority is on re-issue since you have only 2 week to do it before expire.

- If you are happy with your current squad you can leveling event / new girl later.
If you not content just choose who you want to leveling her.

- If count on TP most gacha girls are stronger then event girls.
But TP not everything. The passive skill is what you want to consider before select your girl.

- Gold / rainbow skill bloom in store is what you have to trade if you can afford.
Gold / rainbow dress bloom is something you have to buy with real money.
Our lazy DEV do put Gold / rainbow dress bloom for trade in shop from time to time
but with very high price.

- Life crystal will be more important in future with many stuff you can trade with it.

- I don't have comment about world defence map.