I didn’t get far learning any language using free online resources (technically English, but that was/is rather a passive learning experience).

I mostly used Duolingo to take the first steps and to challenge my interest for the language. At a certain point I prefer language-specific services, e.g. for Esperanto there is lernu (I stopped that, because I hated a few concepts of the language).

I learn Japanese on and off. I’m currently at my third or fourth attempt I believe xD I tried a lot from (again) Duolingo, JapanesePod101 to Memrise. On the long-term I prefer to use online resources secondary, e.g. existing Anki vocabulary decks to guide my textbook. And for a language like Japanese I like to use different kinds of dictionaries, articles and historical context, because sometimes there simply isn’t a definite answer T_T