>>71165412An hour is really all you need imo. I don't think I've reached an hour of Anki yet, at most it's been about 30 mins, it really depends on how well you retain the info though. Learning the grammar and immersion will be a nonstop thing. You can split it up throughout the day, too. You don't HAVE to do it all at once, but that might give you more structure, who knows. Whatever works for you.
If you're already watching anime, playing JRPGs, and stuff like that you're already getting SOME immersion.
Someone else might have a better answer for you cause I can only speak from personal experience...