Please always tip at least 15%, regardless of the service.

[Kimchijeon]

29. Husband and I always tip 20-30% minimum, you just have to factor it into your meal cost

Or delivery driver tip cost. It's just part of the shitty system and you have to suck it up.
If you can't "afford" it, then frankly you should just go get some cheap shit from the dollar section of the grocery store and eat that, because you can't afford to "eat out" or get delivery.

All the more reason to mandate a higher minimum wage for all workers. It's not fair that service workers are treated with less rights and dignity.

Until that changes, you just have to add that extra amount onto whatever your meal/delivery cost is. That's just your total cost.
THEN, if something is extra amazing/special, add more.

Example: We love our local pizza place. It's usually 20-24$ for food. We always do 7$ at least for tip included, but more if warranted or just because (like crummy weather, a holiday, something special- then 10-20$)

I hate hearing people whine "that's so expensive"...yeah, eating out or ordering delivery is a fuckin' treat. Don't treat service people like garbage. Because frankly, if you are in the income bracket where tipping properly financially hurts you, then you are in the same boat as that service person and should feel some damn empathy!