This is my 2nd, so we have everything we need except a second cot.
With my 1st, the only thing I bought at around 14 weeks was a pregnancy pillow and a couple of good maternity bras, as I didn't want to jinx the baby.
I started to do some research though, and we tried to pick up some bigger items at sales or clearances after week 24, also got plenty of things second hand and hand-me-downs. We had the nursery ready at around 38 weeks (but we moved house at week 30 or so, so we didn't want to buy a lot of things beforehand). Also, once you know the shops and figure out what you need, you can pick things up as you go along - they sell a lot of unnecessary things.