I would get a multi pack of 7 pants, 7 socks, 3 pairs pyjamas, 3 leggings/joggers, 3 t shirts, and a couple of jumpers initially (and a coat if still cold). M Lots of children don’t wear the size clothing for their age, so maybe get say 2-3 and 3-4 for example. Shoes can be tricky, as the size they are wearing currently may not be correct, so if you can get a foot sizer online then you can measure them at home once they are settled.
Unpack them, don’t leave them in packets - pop them in drawers to make it feel less clinical.
Then top up once you know what fits and works. Many children (even older children) have accidents during the day and night due to trauma, so you may need more if this is the case. Ask the social worker, and be prepared so there is no embarrassment or rushing around to find spare.
If you can ask the social worker, try and find out favourite colours and characters or themes (eg Bluey, unicorns). New bag is such an important idea. Clothing aside, also try to have some of their favourite snacks or foods in if possible - no matter what this is or how healthy or unhealthy it is.
Children going into foster care may be overwhelmed by too many new and unfamiliar things.
They also may wish to keep wearing whatever they arrive in, or what they bring - even if too small/worn. It’s familiar, and theirs. They may bring teddies, toys, or blankets which need a good clean, but don’t push this. Again, it’s familiar and theirs. I remember sitting with a toddler whose Mum had gone AWOL from an appointment and left her, waiting for a social worker to collect her. She had a blanket and doll which were filthy and stank of stale smoke and grease, but she was attached to them and wouldn’t let them out of her sight for weeks after she went into foster care.
I hope all goes smoothly.