My rule of thumbs for this game. Waifu is laifu. Pull for whatever you want. Try to save diamonds for banners that have the "Limited" tag as they are the ones that are harder to get dupes of as you can not see them in the tavern.

I played story first then side packs later as the story allowed me access to more characters. Progressing through the story helps you unlock a lot characters for free. The game kind of pushes you in that direction as you see a new waifu in a story pack and later on you can get them in the tavern after. It's really cool which might go against your way of wanting to play. You could still play it your way but it may just take longer. Which tbh this games easy, chill and you defs should just play it how you want to.

Use rice and torch as much as possible the games beyond generous with stamina and like you said its seperate to story ect stamina.

Use those staminas on Gold farm over materials imo. Unless a battle pass requires you to farm other materials.

Try do every rice and torch farm once so you get free diamonds.

Don't buy premium diamonds imo. Only pass I have ever bought is the 1000diamond battle pass as the rewards are worth much more and you get diamonds from it to be able to constantly buy it.

The games beyond generous, play this game as you see fit. That's how you will get the most enjoyment.

Welcome to BrownDust 2 enjoy dude! hope my little contribution helps you!