It works for some people, but this is a really good way to pick up bad rules. The thing is, if you make a mistake in conversation people (especially Japanese people) tend not to correct you, so you then think its correct. You mind then begins to apply this "rule" your brain formed to similar situations, which may or not be correct (I started adding だ in to a lot of places where it shouldn't have gone, for example, after hearing it in conversation). Once you've formed this rule though, its really hard to correct - even after you realise its wrong (In conversation I still accidentally add だ in out of habit, then have to correct myself). You don't have to be a grammar nerd, and you don't have to be the guy who can write 2000 kanji but have trouble in day to day conversation, but if you can just look over the grammar patterns and understand them (it doesn't take long) you will have a much easier time further down the track. I know the aim right now is easy communication, but you will get to a point where if you can speak fairly well, Japanese people might get annoyed at you making basic grammar mistakes.