I always try to get as many skills at the top as I can. Those are the roles you'll be making most often and having lots of low-level skills just doesn't seem worth it to me. You'll role them less and you'll succeed less when you do, imo.
to use Mr. Death's example, you'd be rolling your two most important skills at +4 and +3 until you have at least 2 significant milestones. Then you have 1 skill at +5 and one at +4.
Meanwhile, that whole time, you could be rolling those important skills at +5 from the get-go.
I find It really depends on the GM, though. Some GM's have a minimum 3 shift threshold for maneuvers/declarations. I find this, generally, makes having skills under 3 useless - or, at least, almost never worth it.
Other GM's adjudicate those differently, making low-level skills useful. In which case, having a few more +2's and +3's lets you do more.