Sources for self-study?

I’m on my second year of learning Japanese with my school, but we pretty much just use Rosetta Stone, and I’m serious about learning, since I think it would open up a lot of career opportunities in the future. I use this one website that tests Kanji and has different “grade levels” and currently I’m in 2nd grade territory. I also use this one website with a bunch of elementary school level worksheets, all in Japanese, which helps a lot, but I feel like I need a lot more of self-studying to make significant progress. Problem is, I don’t have a clue as to where to start. This question has probably been asked a thousand times, and I apologize for that.