I’m also trying to learn some japanese.
I would highly recommend both crunchyroll and the free site Duolinguo.
I also know that the free, legal video site TubiTV has some japanese things on it. The site obviously, being both free and legal, doesn’t have much great stuff, but there’s a few gems in the ashes. They do have some japanese, and an anime section, but if they can get the dubs, seems to be their preference.
I’d do a mix of structured learning and learning from media. Like others have said, there will be the necessary idioms in the media that you’ll need to learn, buuut… you’ll go through a lot of time trying to extrapolate grammar rules if you want to say something in a conversation that is not said in the media.
One warning on the media stuff…sometimes subtitles aren’t great if you use them to start. Always make sure that what is being said is truly the words on the bottom of the screen. Sometimes, the meaning is the same, but it’s not a direct translation. I’ve seen times when vocal sounds like our “mmm-hmm” “ummm…” “hmmm” are translated into actual words that fit the situation.