I started learning language independently without any background knowledge of my target language. For me, my mentors have been my most valuable resource. Together we have remote, live sessions where we have topical conversations/role play (at the market, at a restaurant, on the farm, etc.), work on specific parts of language (tenses, etc.), and practice proper pronunciation. When our schedules do not align, we hold more passive conversations via text and voicenotes. At the same time, throughout the week I try to work on written compositions which I record and then send for feedback.
When I am studying on my own, Anki has been the most useful resource for building and reviewing flashcards (words and phrases). It’s a free app similar to Quizlet, but I find it better designed for learning. One feature that is particularly useful is that it allows you to add audio clips. There are also a lot of YouTube videos that have been helpful and, although outdated, some chapters of the Peace Corps manual and FSI manual have helped me grasp certain concepts. The most important thing for me is to keep activities diverse – sometimes I will bring in TV shows, children’s books, social media, cookbooks, etc. that are in my target language to keep things interesting. Aside from diversity, making sure to set aside a little time each day has also been helpful for me for retention.