We divided things up roughly by trimester, or loosely into three categories:
- before 12 week scan
- second trimester or before 20 week scan
- third trimester or after 20 week scan.
Before the 12 week scan, we bought stuff for or changed stuff in the house that we wanted to do anyway, regardless of baby. This gave a nice timeline and it was all stuff that felt helpful anyway, as either the things we bought weren't baby-related but mighr make our lives easier when we had a baby (like a microwave) or the changes we made (like painting the downstairs toilet) were things that we wanted done anyway but might get pushed to the bottom of a to-do list if there was a baby around, so good to get done before.
I was quite nervous before the 12 week scan (still am, honestly) and it was a good way to feel I was getting organised without buying baby stuff. The only baby things we bought were two vests, which we got to mark the day we first heard her heartbeat!
Between the 12 and 20 week scan / in the second trimester, we agreed to continue some of the same types of things and did a bit more prep. without really buying many items - we cleared out and painted the baby's room, researched and chose (but did not buy before 20 week scan) a travel system/pram etc. Bought a changing bag. Bought a couple of very neutral vests and one adorable pram suit. Chose curtains. Researched cribs and narrowed it down to a top three so we can see what deals there are. We know we're having a girl but we wanted to keep it quite general still.
We decided to buy big items mostly in the third trimester, but start earlier from the 20 week scan to allow us to spread the cost a bit. We actually got the pram at 21 weeks when we saw the one we wanted on a great offer. Ordered the car seat too as part of a package deal. That's one of the most expensive things we'll buy so we'll take a few weeks off from big things left like crib/cot/chest of drawers, but may start to stock up slowly on things like nappies from now.
No idea if this is helpful to you, but staggering the purchases into stages really worked for me and let me feel I was still planning and getting excited early.