Lansinoh nipple cream - I only needed a little for a few days but would have sold everything but the baby during those days!
Sleeping bags. Especially for fidgety babies.
When they're old enough, only buy calpol with the syringe. Can administer one-handed & no spillages.
Vibrating chair rocker thing. Godsend.
Muslins. Lots of them. Keep a 'spare' in your bag - can be an impromptu nappy, blanket, hat, sun shade, change mat, play mat, etc.
If you want to express I heartily recommend the medulla swing pump. I didn't get until a few months of struggle. Was worth every. Single. Penny.
I wanted to try reusable nappies & found thenappylady the best place for info & supplies.
We bought & still rave about reusable cheeky wipes. They are so much better than disposable wipes & save you loads of money.
Agree with the Aldi nappies - I was really impressed but did miss the boxes the pampers nappies came in!
Also - sod disposable breast pads. They are noisy, sweaty, and expensive. I used amazing reusable ones that were invisible & silent.
Second hand furniture, pram & clothes really cut down the expense. NCT sale in a 'nice' area will get you good quality stuff.
Good luck!!