Blogging as a form of self-promotion requires more ongoing effort than most people realize at first. With that said, depending on how much time and effort you're willing to put into it, you can use a blog as part of a content marketing strategy to establish yourself as an authority within your realm of expertise.
Ideally you can launch your blog with at least 2-3 pages of posts already written up - about 10-15 posts overall. This gives the people discovering your blog when it first launches plenty of material to dive into and decide if they want to subscribe to updates. It also gives you a taste of writing more than one blog post on a single topic, so you can find out if it's something you want to do before you start doing it publically.
Email marketing and blogging go hand in hand in content marketing strategy - you start building a list of people that like what you have to say, and let them know when you've posted something new so they don't forget about you forever. This is a major part of converting readers to leads - If you're careful and do it responsibly, you can send the occasional promotion and/or notice of new services offered to this list. Everyone that gets the message appreciates your expertise enough to get updates on what you say, so they are some of the people most likely to act when you say you can take care of a problem they have.
The trick is writing about your realm of expertise in a way that your target market is likely to come across and appreciate it. I've found some really great configuration tips and nuggets of wisdom on tiny blogs over the years through Google - but if I'm looking up tutorials on how to configure something myself, I'm not super likely to convert into a client.
Yoast is a great resource on some basic SEO and content marketing stuff... and if you end up blogging on WordPress, Yoast SEO is the gold standard for SEO optimization plugins. On a relevant sidenote, the previous sentence is exactly what effective content marketing can do for you!