Our first two were suprises, and i had no problem with what to buy! Still found lots of neutral stuff, maybe just not the traditional ones (hate lemon and green !) Grey, white and red are very common now and are great neutrals.
I was convinced DS was a girl, and will admit to the slightest moment of "no, you mean girl" when he was born. But it didn't last once he was "really here".
DD was an elective CS due to breech, so we were very happy to still have something a suprise! Both received so many gifts that were gender specific that it didn't matter what i had bought before and it was a bit easier knowing the right size to buy anyway.
This time we did find out; because i wanted to know which items from DS and DD i could give away, who would need to share a room, and how much new stuff i might need. Also to help prepare DD for the idea, as she doesn't like change at all!! There will be 6 years between DS and this baby, so i think it is probably good that she's a girl. Also, DH and most of both our families were firmly convinced she was another boy as he has so many boys in his family so were actually shocked to find she's a she!!!
I think it's a very personal decision, just like lots of things about PG and babies. I have found both to be right for us at the time, and can honestly say that i'm looking forward to this bub just as much as the older two
Good luck with it all