Oh god.
I recommend getting the basics of the language down first: hiragana, katakana and basic grammar.
Then I would start doing anki to build up vocabulary knowledge (a consequence of this is that you also learn kanji... eventually).
There's a frequency deck with the 2k most common used words in Visual Novels, that's a good place to start.
Learn around 10~20 new words a day.
As you find new words that aren't in your deck, make anki cards for them. There are good tools for this.