I guess you are asking: What will be the effect of changing your domain of your blogger’s website on SEO and the traffic?
So let’s break it down:
1- Google will consider your custom domain as a new website the day you change the domain of your website. Hence, it will have a significant impact on traffic in the initial days so months.
2- changing to a custom domain doesn’t highly impact your on-page SEO, there will be minimal impact on Onpage SEO even the domain name is changed. Your on-page SEO depends on your content and how you master the SEO. The only important point that needs to be taken care of is the URL structure in the new domain should be the same as the old domain. example : (blogname.blogspot.com/2021/02/1hacker-is-thebest
) needs to be (blogname.com/2021/02/1hacker-is-thebest
)
3- Google will take its own time to crawl, index any new website and URLs before it ranks them, therefore, there will be an impact on overall traffic.
4- You will need to add your new custom domain blog to the search console, submit a sitemap, and request indexing.
5- When you will change to a custom domain try to do these steps:
a- Update the old backlinks with new URLs where possible and Update internal links with the new URLs
b- Edit article contents and improve its quality (Add natural meta descriptions, alt tags, etc.
c- Write fresh content regularly to speed up Google crawling and indexing.
d- Regularly monitor keyword status in Google search
e- Check index status of your urls in Google webmaster console
f- Look for broken webpage links or 404 errors use ahrefs.com
28/02 edits: I forget to mention You need to confirm you own that custom domain in the search console, by taking a code and paste it into the DNS setting in Goddady or whatever service you buy the domain from then change the address of your Blogspot to the custom domain you already added to the search console, so after that, you will see a notification about This site is currently moving to www!domaine!com. You can check youtube on how to move blogspot to custom domain in the search console
In the end, I guess that’s it, hope it’s helpful, and don’t worry you are still in the beginnings of blogging, you can manage to make things work great since your blog is new and hasn’t high DA (domain authority) and PA (page authority). Good Luck