Writing can be a long, tough but rewarding thing todo, my advice would be to setup a blog website first off, ones like Wordpress, or Blogger all offer free accounts for you to create, you will then start building up an audience that way you will see who your audience will be when you start writing, use the blog as a template and a starting goal to writing - good luck !
For those young generation, I believe to review those latest Tech product will be attractive. You can review them in the form of Video or Text & Pics. The Youtube reviewer is now the most popular job on the internet, but make sure your words are attractive and interesting enough which is essential.
This day in age, start by having your own blog or website. You can grow your business from there. Be consistent with your blog and after it's set up, make sure you post a new article at least once a week. Interact on social media like Twitter, Facebook, Instagram (depending on what you're writing about), and Pinterest (depending on what you're writing about). You will gain an audience, experience, and confidence from having your own blog. While you're building your blog, you can begin pitching places with your writing. I really wouldn't write for free on other people's blogs, websites, and publications if you can help it. You're better off spending that time building up your own website. While you do the above, I would also actively search for work as a writer. I found a good article with some tactics I've used with success in the past. https://elnacain.com/blog/20-ways-find-freelance-writing-jobs/ You may spend a couple of months feeling like you aren't getting anywhere but don't give up! My first year as a freelance writer I made $60. My income grew from there. After about a month of writing 5-10 pitch letters a day sometime after that first year, I finally got my first really good paying assignment. If I had given up I wouldn't have been where I am today. For me, it had always been for the joy of writing and eventually the money found me. Good luck! I know you can do it.
Start writing articles on all these topics. Create your own blog on wordpress, this gives your a platform. Publish your articles here. Find other bloggers who write on similar topics as you. Talk to them, get advice from them. Find some freelancing work online, small projects that you can handle along with your primary job. Happy writing!!
I remembered when I started my writing career several years ago, I took the time to learn everything. I build my portfolio by setting up a personal blog. I also write on Ezine Articles to promote my blog in different niches. I tried Fiverr gigs who are looking to publish on Ezine Articles myself, and that's where it all started. Until now, I'm enjoying my writing career serving few clients for my guest blogging service. Keep learning and improve yourself.