The problem with this type of question is that you're assuming that there is a one-size-fits-all "standard" answer for all types of sites regardless of how developed they are.
You have to understand that at the end of the day, guest posts only make sense for sites that get organic traffic.
The rest are basically paid link-building techniques.
There are tons of offers here for that kind of thing.
But if you are looking for better results, you should focus your guest posts from sites that already have an organic traffic flow.
At the very least, sites that have over 100 or 200 organic keyword mentions on SEMrush, that's a good rule of thumb.
But you'll also have to pay attention to how well those organic keywords rank and what their probable traffic flow is.
Ideally, you should just focus your firepower on finding the most dominant blog in your niche and try to get a guest post on that property.
It's going to be a tall order, but when it comes to return on effort, that may be worth it.