I started learning Mandarin last year and these are some of the resources I've found most useful:
Apps TOFU Learn - An app like Skritter for learning to write hanzi, but free. Has word lists grouped by HSK level for simplified and traditional characters
Hello Chinese - An app like duolingo but focused explicitly on Chinese. It's really good for getting started. If I recall correctly, the free stuff goes up to HSK 2 or 3.
Du Chinese - An app to practice reading. It has toggleable pinyin over the words and has two kinds of translation: you can turn on translation for sentences at a time to show up at the top, or you can hold down on a word and get just it's definition. Readings are graded from Newbie to Master in 6 steps and kinda follow HSK. It also has colored underlines for words to show their HSK level. This is one of the best ones on this list once you have got pinyin down.
Pleco - A dictionary app. Absolutely mandatory for learning Chinese.
Hanbook - Another dictionary app. Not as thorough as pleco, but a bit more user-friendly.
Anki - Flash card app. There is an overwhelming amount of stuff you can do in Anki, but my main suggestion is to get the Spoonfed Chinese deck. It's whole sentences rather than words with native speakers saying what's on the cards. It's around 8000 sentences in order of increasing complexity, I would recommend when starting to turn off the card type that's English to Chinese and just focus on the Chinese to English types.
YouTube Channels Shuo Shuo Zhong Wen - A lot of beginner-friendly (HSK 1-3) content presented mostly in English.
Grace Mandarin Chinese - A lot of beginner-friendly (HSK 1-3) content presented mostly in English.
Everyday Chinese - Beginner to intermediate content (HSK 2-4). Presented mostly in Mandarin with English, Pinyin, and Hanzi subtitles.
Mandarin Corner - Beginner to Advanced (HSK 2-6). Presented mostly in Mandarin with English, Pinyin, and Hanzi subtitles, with English-free versions in the old episodes and on their site. HSK prep lessons as well as videos exploring China and explaining what she sees around her. The story-based learning from the exploration videos are top-notch when you get to around HSK 3.
Shows
iPartment (爱请公寓) - It's a sitcom based in Shanghai and is pretty Western, so you can understand what's going on even if you don't speak any Chinese. Read the synopsis on Wikipedia if you're in this boat. I watched it before I passed HSK 1 and picked up a few things, but there's certainly value to just listening and getting used to how spoken Mandarin sounds. I went back once I passed HSK 4 and started watching it again and was able to understand a lot more of the "Why" things were happening.
For movies and shows, check out Language Reactor. It's a browser plugin for Netflix and YouTube that offers better subtitling and translation.
Similarly Chinese Zero-to-Hero has a similar feature on their website.
I might come back and add more to this when I'm not on my phone.
Edit: I just realized half of this fits in the other thread, oops.