I agree that you should strive for an overall complete application, but I disagree that one aspect isn't more important than the other. Recommendation letters are more important. As far as which school or program, just apply to a whole bunch of them.
But the OP is lucky is he thinking about grad school now. That's a head start. I didn't decide to go to grad school or even think about it much until my senior year, so I didn't have the luxury of thinking about what would get me into the best grad school. And so my application was probably weak, with the exception of my recommendation letters and grades in upper division math. And that was enough, although I only got into one school out of 5 (pretty high ranked, but below Ivy League level). The thing is, if you have talent and someone notices it, they will want you. That's what those recommendation letters can do for you.
But I'm not saying you should just impress 3 profs and just slack off on everything else. No, do your best at all of it. But impressing the 3 profs has to be the top priority.