How to get started writing content?

I have written content for various websites and been paid sometimes, but I am now trying to make writing my full-time gig.

I have joined sites like Upwork and the Content Mills for writing, but I am told these are a waste of time.

How can I break into the industry and start writing? I realise that I will have to start with low rates.

Any advice greatly appreciated.

The first thing to do is to writing as much you can. If you have a degree in writing or similar major, try to find a job offline like local newspaper or advertising agency. Having an offline job will help you get stability before you move full-online and get you constructive feedback to improve your writing.
Upwork is a waste of time if you are going to write for small gigs and websites. You will get paid less than you are worth, always. But, it is also an excellent platform to get high quality and high paying jobs. Follow Upworker like Danny Marguiles who makes thousands of dollars on Upwork from writing jobs.
Complete your profile 100% i.e. build a portfolio, submit your academic documents, and get some certifications (HubSpot is a way to go). Don't limit yourself to just to upwork, there are lot of others which are more awesome (IAPWE, HubSpot, and Freelancer).
If you have a budget, stay on BHW and open a marketplace for your great content. There is a huge market for great content on BHW.
If you are looking for quick money, go to listverse.com and write listicle for them- they pay you $100 for 1500 word article. I wrote so many articles for them in the past.
Welcome to a great industry, and good luck with your career.

That's great advice. Many thanks.

Guys, do you use Grammar.ly? I am not a native English speaker but I think that Grammar.ly is a good tool for everybody not even for us foreign speakers.

I find Grammarly to be a question of style choice sometimes. The errors that Grammarly points out are not always errors in my opinion. Just a matter of personal style.

I'm a writer too and I can tell you for free that so many other writers face the same challenge. Have you tried cold emailing? It has worked for me before. It may work for you too.