Japanese is very easy in the beginning. The basic grammar structures are easy to grasp, but when you reach an intermediate level it all goes to hell from there. I learnt hiragana and katakana in around 3 hours all up. I also would recommend learning the phonetic alphabet and then start grammar. Begin kanji after you have basic grammar covered. For example when you can say "I went to the park. It was enjoyable." in Japanese. This is how i was being taught in my first year of university. Grammar is more important than kanji. I have learn't alot of grammar and know only 360 kanji. By the end of my university semester i will know 400 kanji and i will go on to advance units. Also it is more exhilarating when you can comprehend the language even if its just a little bit. I still remember how fun it was saying これはえんぴつです。
tl;dr Japanese grammar and vocab should be priority over kanji. Ease into the kanji after basic comprehension of the language. You will feel like quiting every other week when it gets hard, don't, just persevere.