Supermarkets tend to do multipacks - big multipacks of plain white vests and babygros, packs of 3 of patterned ones, Mothercare, Boots, M&S, John Lewis and Next also do 3 packs of babygros. For some reason the coordinating vests seem to come in 5 packs. I was always very particular about vests & babygros 'matching' although I've no idea why, just made life harder for myself!
I would say that it might be worth getting a few from different places, as the sizing is far from standard! For example, on my DD Next & M&S come up huge, Mothercare a bit smaller, Sainsbury's a bit smaller again, and forr her Asda and Tesco are true to size. She's 8 months now and the other day was wearing a 0-3 month M&S babygro with a 9-12 month Sainsbury's cardigan,, both fit her fine!
With vests they seem to come as short sleeved (standard, most are like this), sleeveless (pointless for a winter baby), and long-sleeved. In the depths of winter my DD had a long sleeved vest under a babygro, day and night. I'd save my favourites for daywear. She didn't wear outfits or tops and leggings until she was about 3 months old and still regularly wears babygros as they are so easy and comfy.
Ebay bundle, NCT sale or the supermarket. The advantage with second hand is that they are all softened up by repeated washing, no fabric factory chemical residues left, and you can see how well stains come out.
I can't see that anyone else has advised this but sorry if they have and I just haven't read the other post carefully enough. I would really recommend sleepsuits with integrated scratch mits. I now you can but separate little mits but they will not stay one.
M&S, john lewis and mothercare all have integrated scratch mits for their sleepsuit which are just like little flaps that you pull over the baby's hands.
Newborn babies are suprisingly scratchy little things....
DD has a range of vests and babygros from everywhere i.e primark, asda, tesco, next and I've found the quality of all have been good.
With regards to attached scratch mitts, morrisons babygros have them too (well the one DD is currently chewing on does)
Definitely get a range of sizes too! DD was an 8lber and in newborn for about a month but still fit into some 3-6 month vests. Plus they grow out of them that fast, it's better to have a range in case you fall short.
Make sure you buy 100% cotton ones. Also re colour - my little brother was allergic to certain colours (or more specifically the colourant) - in particular red. So I've bought everything pale - especially the vests/bodysuits.
We bought mainly 0-3m and 3-6m, with a couple of newborn (they grow out of that straight away).
For vests, ones that have poppers over the front (like these) are very useful for the first couple of weeks - you don't have to pull them over their head or pull them down to get them off.
For sleepsuits/babygros make sure you buy ones with poppers on the front - don't buy the ones that close at the back because they're a nightmare to use (baby needs to be put on tummy).
Where to buy - we've bought a mix (mainly on sale) from Primark, Tesco, Asda, Next, Mothercare etc.
As others have said I wouldn't bother with proper outfits for the first few months. Babies hate being in them anyway - a sleepsuit is a lot more comfy.
Not sure about the terminology, but I much prefer the sleepsuits/babygrows with no feet in them. You can use socks instead.
Reason is that they fit for longer. Apparently you can't have the toes pushing against the ends of the ones with feet in as it's bad for their feet. If your baby is a bit long and not chubby you might find there is no stage when they fit the ones with feet without this happening. If you put them in a too baggy sleepsuit/babygrow their limbs sometimes come out of the legs/sleeves and get caught up in the body part.