Hard to tell because we all have different taste. But maybe you can start with:
@teamsteem
@jerrybanfield

Then go on Google and search about Steemit topics you want to learn more from: where is money coming from, how the upvote works etc...

Go on the trending or hot section, select a tag that interests you and check for quality posts about that topic. If a topic does not show in the list, click on any topic and in the URL change the topic manually, for example:
https://steemit.com/trending/introduceyourself
Can be modified to
https://steemit.com/trending/vermicomposting