Should I Summon For Katarina?

Will having another red mage help your roster significantly in PvP and PvE content? At least wait for the legendary banner. These rotational banners have quite a long timer unlike legendary.

When it comes to these banners with older units, I usually follow the rule, that I'll eventually get all of them as pitybreakers on various other banners. You should wait for Nowi if she's your goal. Also, Kat is sharing a focus color with Eirika, which is quite risky to say the least.

Decide only on the 28th.

Do you like her?

If no, then no.

If yes, then yes.

If yes, w8 for L Banner, just like 3 days, coz you may like your new legendary hero more. :)

Also, H!Nowi i cute af... rly... i just have her -spd+def, so it sux.

I would say wait until we know who will be on the Legendary Banner. I'm doing the same thing with Flying Nino as I want a powerful green flier (I have Spring Camilla and Bride Sanaki, but both are -ATK) and didn't get her in my free summon circle. However, I don't know if Bride Tharja or Karla will appear on this week's LB, so I have to wait until tomorrow night to make a choice.

Probability of successfully finding H.Nowi on Halloween Banner assuming pity rate never increases:
50%: 140 orbs
60%: 185 orbs
70%: 244 orbs

Expensive unit to pull.