Being a new father myself (4 month old currently) these are my top items:
* Baby Sleeping Bag - ours wriggles like mad so blankets are pointless, these are amazing.
* Teething device - because when it comes, your need it big time
* Underlayers - get more than you think you need.
a general note with clothing , look at button placement. Sounds stupid but some clothes companies really haven't thought about their products at all and have buttons in so many awkward places that in practical terms its beyond stupid and likely to wind up the baby as you attempt to button them, or take their clothes off in a rush! Buttons at the front - great, at the side - passable, many at the back - avoid avoid avoid.