This one is a super oldie but goodie. It's a fully featured html editor. The programmer is a great guy who just puts everything out there for free.https://arachnoid.com/arachnophilia/
I started my web design learning on his editor and though I now use the standard for development, Dreamweaver, his web editor is a fantastic place to start. Lightweight, simple but offers all the basic tools you need to do slim and clean pages along with CSS.
For graphics and such though, you're best off just biting the bullet and paying for illustrator and photoshop as they offer so many conveniences that you're just shooting yourself in the foot not to use them.
If you absolutely must use open source/free, gimp is probably still the gold standard for free photo editing. I'm not familiar with free vector programs but there is probably a companion tool to gimp that does the same stuff for vector.
Someone mentioned wordpress which is alright but I warn you: It requires constant maintenance. If you leave your wordpress site alone and online for more than a few months it WILL be hacked. Exploits are constantly being found and random teenagers are always scouring the web for outdated WP plugins.