Guest blogging should be done at which stage?

You should be writing it yourself if you're new to it -- you need to build your voice! -- unless you have access to high-profile guest bloggers whose posts can potentially draw more attention to your blog in its early days. They can promote their posts throughout their own networks, which in turn puts your blog on the radar of people who follow them.

At the beginning, you should spend 70% of your time contributing great content to other blogs that already have an established community, and 30% of your time ramping up your own blog. As you grow your community, shift that ratio to focus more on your own blog. As you establish your expertise in the space, it makes attracting quality readers to your blog that much easier.

It is unlikely that others will want to write content on a brand new blog. Typically, the blogger must create quality content for a specific topic and build an audience first, and only after that will others be willing to write guest content for you.

There are 12+ million established blogs and probably 30+ million installed blogs. There is almost no benefit to other writers to spend time writing for your site. They are much better off writing on established sites or creating their own authority content.

I agree with the others that you need to build your blog with your own content first. Once done, you can seek out communities such as MyBlogGuest, where like-minded bloggers find guest blogging opportunities - and you can find others who may want to contribute to your blog. But anyone you find to guest blog at this point is probably not going to be very high quality, if you don't have your own content.

Most blogs accepting guest posts look skeptically on content that is too promotional. Once you know what you are trying to accomplish, the next step in our guest blogging guide is finding a site to target. This means choosing a specific blog you would like to be published on. It is best to start out by generating a list of potential target blogs, which you can narrow down later. You can also use Google to turn up good guest blogging opportunities. Once you get some targets, you will want to look for sites that clearly accept guest posts. This should be the blog that is best positioned to help you reach your goal. To do so, you can write up a guest post proposal. This is typically a short email that lets the blog know what you would like to write about. If the blog you are targeting has a dedicated submissions page, you will often find an email address or contact form you can use to send your proposal.
You can read more here: https://themeisle.com/blog/guest-blogging-guide/
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath