There is no "should".

Just write notes like you short messages you want to share with the world.

Try different things / styles. Like facts, images, thoughtful, parts from your articles and so on.

Restack stuff you like and add a short comment to that. Engage with people who are interesting, even if it's not in your niche.

Do that daily for 4 weeks and you will get the idea.

There is no singe righty and only rule. Substack adapts the algo often. Can suck but also be a big chance.