If you are looking for how to build an online presence for free, you can do that, but I highly recommend that you purchase a domain name of your own. There are a few under $10.00 still, some a little higher. But whichever you chose, remember to stick with it.
Still, there are free domains. I would not recommend them, but they are available. But don't get a subdomain on someone else's domain. The one exception would be a Google blogger bog or a Google site, because the subdomain you choose can eventually be set to send people to your own domain.
Those are the only places that I will recommend for hosting a free site/blog, too. Everything comes at a cost, even when it's free. Google blogger/sites will slow down at peak use hours. But at least they don't require you to show ads. Then again, you could write valuable content and show ads on Blogger and Google will pay you a share of the advertising money they get when someone clicks on an advert.
I don't like ads, which is why I stopped playing around with Wordpress.org, Tumblr, and others. Plus, you get nothing for the adverts shown, even when your user leaves your site by clicking on an ad.
Dedicated Ad sites are called scraper sites, usually. They are only built to entice traffic and show them an advert and get paid for when the user clicks the ad. It requires a lot of traffic to make that work, and then again, your domain name would need to be a good one, usually. That means, get a really good domain as soon as possible. It also means you could get an expired domain name that already has traffic relevant to your website topic. But these usually require more than a registration fee, there are drop and catch services dedicated to grabbing such names and they usually fetch a nice chunk of change. It's not free, but it is an option, and once you get going you will probably want to do something like that, or grab one from the domain name board, or a domain name forum.