I recommend the upcoming sales! I found out I was pregnant this time last year, I was 6 weeks by this point, and I got some real bargains. Especially winter clothes, so get a few wintery things in size 3-6 months. Also check out boots, they have good sales on, well at least the big one in birmingham did for me last year, I got a bouncer, changing mat and something else I can't remember for 1/3 of what they were meant to cost.
Erm.
Otherwise, we waited until 20 odd weeks to buy the travel system but that's just when we found the one we wanted and found it on ebay at a bargain price... we wouldn't have minded waiting longer but it had to be bought at some point so then was as good a time as any.
Just get bits as you go along so that you don't get lumbered with a big bill all at once. Don't get too many newborn size nappies as they aren't in them for that long.
Good luck with your pregnancy x