It's awesome that you're thinking about blogging. It's yet another form if self expression.
How much space or web traffic do you actually need for blogging.
This question was posted in reddit recently and is perfectly valid one.
What does a blog post consist of?
It's text, images, files that belong to a CMS system that you use.
If you use WordPress it's under 20MB in size. When you install some plugins for various tasks the website could go to about 250MB
If you include multiple photos per blog post that will also add up to the total disk usage because WordPress creates several versions of each photo (depending on the theme) so it can load faster on desktop or mobile. A photo from your phone is between 1-5 MB. More professional cameras it's higher.
The next thing is web traffic. Nowadays most hosting companies offer close to unlimited amounts of GBs. We're in 21st century after all.
If you're just starting with your blog the traffic will (hopefully) increase over time. That means that you're doing something right.
The traffic depends on the blog article's content, plugins and the theme that your site uses.
In conclusion I'd say start blogging on your own domain and pay $5-10/mo for a good hosting and think more about stuff that matter much more such as growing your business, online presence & reputation 🙂
See Grant Cardone's books & talks. You're welcome.