Mandarin Companion is an awesome resource. They're not free, but at $8 USD for an ebook are very affordable. The whole series is really fantastic. https://mandarincompanion.com/products/in-search-of-hua-ma/ for example uses only 150 characters. As you get started, a very reasonable goal in the first several months of learning would be to be able to read that.
https://www.amazon.com/Fluent-Forever-Learn-Language-Forget-ebook/dp/B00IBZ405W is a book that really shaped how I approach learning - focus on pronunciation and learning key nouns and verbs, make your own flashcards, and don't worry to much about grammar - instead worry about conveying meaning, and let the grammar fill itself in.
I know they're not free, but they were so essential to me that I have to recommend them.
Now for free stuff:
- Coursera has some good courses: https://www.coursera.org/learn/hsk-1? for example.
- http://www.hellochinese.cc/ is a really nice Chinese specific app.
Really though the best advice I can give is to set a specific, achievable goal for yourself, and then work toward that goal. For example "I want to be able to read In Search of Huama out loud" or "I want to be able to order my meal in Mandarin at at a Chinese restaurant".