Which banner should i roll for right now

Depend on what servant/class you need right now

I need more context for what you need gameplay wise, maybe list of gold servants and such.

Right off the bat in around a week archer arturia comes out and is one of the best archers in the game second to only possibly Gilgamesh and focuses on spamming her np, but requires supports to achieve max potential she will probably be the best servant you can pickup for this event if you have either waver or tamamo.

Tamamo lancer is good in a general sense, but falls below arturia since her 2 of her skills have pretty hefty demerits such as an enemy np charge and self stun, but she is useful against archers and godly against male archers.(Would recommend rolling for her and kiyohime when she's on rateup if you don't have a good lancer.)

As for 4 stars I need more info since 4 stars need better teamwork and can't function as good without it like 5 stars. But in general banner 1 has better 4 stars gameplay wise.

Disclaimer: Roll on the banner that has servants you want for whatever reason be it gameplay, waifu or just cause you like the art.

If you're looking for gameplay reasons to roll, look at the tier lists on this site and actually read the profiles of the servants you can get. There are several good ones all of whom have setups that help them succeed.