Unless you have a preference on thread count…I have picked my crib bedding based on design / color scheme.  The one suggestion I do have is for the bumper.  For my first son, the bumper was pretty thin and not real firm and did not hold its shape after a few washes.  It was still super cute and functional but for my second baby I opted to spend a little extra cashola for a nicer bumper.  As for sheets, you may want to stock up on a few…they go through quite a bit of "use"  so a lot will depend on your budget.  Organic crib sheets / bedding sets are available but will definitely narrow down your selections.  I did use an organic mattress pad, but my bedding was a mix and match from various companies.  Keep in mind too what style bumper and dust ruffle will work with the crib you choose.  Hope this helps!