Immersion is by far the best method, but you need to be mentally engaged for it to work. Have both spoken audio and text is ideal. If you use immersion the only things you will need to study are basic grammar (like verbs and such) and kanji.
Kanji radicals in the normal sense are useless basically, but it's a lot easier to remember a kanji like 後 if you can remember it as 彳幺夂 rather than a bunch of random strokes.