My motto: Write Daily. Keep everything. Let Posting take care of itself.
1. Write daily. Every day, without fail, I write up and save anywhere from 2-5 "things"--poems, sales letters, articles, short stories, it doesn't matter what. Like old school pen and paper writers, I keep "the trunk" full. That way, when I need something fast, or inspiration, or an idea has marinated long enough, it's there. All writers have a trunk--mine just happens to be a 2TB external hard drive, with full double encryption :-). I even keep the journal in there.
2. I keep EVERYTHING. Because I have been writing 37 years now, off and on--and I have used things I wrote 2 decades ago probably a dozen times in the last few years, when filling orders for clients. Before computers, I had speckled composition books filled with observations, thoughts, aphorisms, and useless trivia (and I still have those notebooks, BTW). You never know when something will come in handy, or fit beautifully with that crazy idea you had 5 years ago, or be the answer to a plothole that has been annoying you for years. So save it all. Digital storage is cheap.
3. When I get the new site operational, in the beginning I will be posting regularly--but it won't be "me" all the time, per se. I already have about 50 evergreen articles in my chosen niche stored away, that can be optimized seven ways to Sunday for a huge variety of keywords. Those will be set up to autopost once a week. "I" will be writing in between, as and if needed--but mostly promoting the site through posting on social media, disqus, Reddit, and everywhere else, and engaging members in the comment and forum sections.
In my experience, your readers will let you know how often you need to post-- if, for instance, your readers fully engage your content with comments, observations, and questions, you can use their feedback to decide what to write next and how quickly to deliver it. My M.O. is usually to under-promise and over-deliver, so people stay very happy. Ideally, you want your readers actively suggesting new topics, and actively asking you when your next post will be live. But it can take a while to get there :-).
At the least, once a month. Preferred, once a week (with no direct duplication multiple places, take the extra ten minutes to manually "spin" your content. simply re-posting the same article everywhere looks bad). Ideally, once a week posting, the rest of the week engaging commentators on your own site and elsewhere while the next masterpiece is patiently waiting to be autoposted LOL.