How did you grow your portfolio?
I recently started the coding course on freecodecamp and I am breezing through html and css. My major worry now is getting the required experience to improve my skills. I want to know how you went about building your skills, gaining the necessary experience and growing your portfolio.
Build projects out of your comfort zone.
First, congratulations on making your way through! I've heard good things and have always wanted to go through it to decide whether it's worth recommending to people (beyond merely having heard Quincy speak and thinking he sounds trustworthy enough...), but never get much past the introductory lessons.
To your question, I hate being the self-promotional guy, but as it turns out, I wrote about this recently on my blog (personal blog, not trying to sell anything) as part of an "as long as everybody is looking for something to do under quarantine..." kind of series, here.
In short, when working on your own, you mostly want to create projects that have a simple mission statement (so that you don't get too far off track), big enough that it'll keep you busy for a while, and interesting enough to you (like something that you'll actually use) to keep you from deciding that watching TV is more fun. I provided some examples that are probably best viewed as a starting point to spark a better idea of your own.
The next installment went (superficially) into getting involved with Free Software projects to build up experience working with other people, among other things.
Good luck and I hope that helps!
Essentially, you come up with something to build, whether it is a personal project or a small client project. If you are proud of the result, you can then add it to your portfolio.