Learning grammar from the beginning is a really great goal! It helps learning new words (e.g.: all verbs end in an u-hiragana character).
On the other hand you will have very little problem with grammar, if you don’t ever try to translate a English sentance with it’s grammar into Japanese. Just use Japanese grammar! It helps!
I’ve learned the grammar with Tae Kim’s Guide to Japanes Grammar (it’s free and it’s absolutely amazing!!). It has a great structure, so that Japanese grammar get’s totally logic!
~T 
PS:Obviously you like looking anime/read manga/hear Japanese music.
The best thing about a good grammar knowledge is, that you can hear a word in a sentance and start to guess.
For example right now i heared “nemuranai” in a song. I know, that it must be a verb in it’ts negative form, that the verb is a godan-verb and it must be “nemuru” in it’s dictionary form. I already heared once a word sounding like that, and it meaned something with sleep. So “nemuru” could mean sleep?!
Than i typed this in Jisho.org and there it is: 眠る, to sleep.
Btw: I also can tell that “sleep” in japanese must be “nemuri” just by knowing the verb.