i think it makes a difference how long you have been out of school, if at all.
ive been out 2 years, so far, and i have 3 pubs -- 2 from my work in college (first author on one) and one from the work ive done the last two years (first author on that one, too).
but it might be unrealistic to think that you could first author a manuscript while in college, and if you can get one, its a stretch i think to assume that you can get two.
that said, its probably more important to know your work inside and out, and know about the reasoning, rationale, etc behind it than it is to present a paper with your name on it, especially if you are NOT the first author.
in addition, about first authorship, its important, in my opinion, to actually have written your papers. sure, you may have gotten help from your PI, but for you to really OWN the work, you need to show that you were a huge part of the actual writing and revision process. it would be embarassing to have your name down, especially as a first author or something, and not know exactly every single point that the paper makes, and all the references, etc.
thats just my $0.02