well my only concern with learning just kanji, is that if i am studying random kanji from my book in the order they have them, (which they are apparently 'systematically arranged') and they dont use them commonly, i feel like ill forget a ton.
but i suppose that goes with anything, if you reinforce, you probably wont remember.
whats probably the hardest part is starting from the complete beginning. i can properly pronounce hiragana and spell what i hear, i suppose thats a start.