Do you think you'll have a shower? If so, keep in mind that you may get a lot of things then, too. With my 1st, I got some major items (car seat, diaper bag, carrier) at about 27 weeks, then had my baby shower at 31 weeks and got nearly all of the other things I needed (clothes, another diaper bag, bathtub, little baby items, etc) - there were only a few minor things I needed to get after that. With this baby I'll probably start getting things at about 27-28 weeks too.
I would start with making a list of what you need to get. No harm in getting some gender neutral/major items now, but I agree that waiting until you know the gender can be helpful in picking things, too.