Keep in mind, HTML is involved with a couple other languages. Here are the paths I would suggest to go with HTML:
CSS - If you plan on building websites, trying not to use HTML is like trying to bake a cake without an oven. I’m sure it is possible to heat the cake batter sufficiently, but I am pretty sure it will be time-consuming and not taste very good in the end. CSS is for styling your websites so they don’t look like a bland, white page.
(OPTIONAL) SQL - SQL is basically a way to manage data, but honestly, I have not used it (and don’t really plan on). I do know it is a way of storing data, so it might be another thing you might want to use.