Textbooks are boring (tried using Genki for a few months learnt absolutely nothing, good job I didn't pay for it). My suggestion, go the AJATT way and those manga you have will be very usefull. In my experience once, it doesn't take long atall untill you can read pretty much anything if you use a dictionary (Including those Soul Eater manga).
All I did:
Learnt ひらがな、カタカナ.
Learnt all the kanji in "remembering the kanji" (If you don't want to buy, I'm sure you can find a scanned version somewhere *wink wink*) (Don't make flash cards for this like heisig suggests, it's far too cumbersome, use an SRS like anki, or
Remember and review kanji flashcards online with James Heisig's "Remembering the Kanji")
Added sentences to an SRS (I used Anki) from
Tae Kim's Japanese guide to Japanese grammar
After this If I used a dictionary I could get an understanding of pretty much any manga I had, any website...
Then after that you can add sentences from you manga or whatever...
