If I start learning japanese studying the hiragana and then the katakana is it a good way or i waste my time? what do you suggest me to learn japanese??
I learned hiragana and katakana first, now I am learning kanji, I think such way is worth to try, of course is not a waste of time because that is the same method japanese use for writting/reading.
I'd say that what you suggest is probably the best way. I always slogged behind on the katakana, but they've become so pervasive in modern Japanese that you're better off learning them up front with the hiragana.
I learned Hiragana in the first week, Katakana in the second, the numbers (which are in kanji) in the third. Now, I've been trying to remember the most frequent and important kanji. It's never wasting of time to learn a language.