@Mumistiredzzzz have you signed up for anything you need to, eg. ParentPay or whatever system your school uses to book before/after school clubs, or their system for booking lunches if your DD will be having school dinners? For reception, they don’t need much else - as time goes on things will get added in (clubs, etc.) so you’ll develop your own systems, don’t worry!
I do a lot of the things already mentioned here. I have a printed sheet pinned up in the kitchen which has a table with each child and the day of the week - it says what each child should wear each day (PE kit or uniform), what they need to take with them (e.g. swimming kit, extra sports kit like hockey stick, etc.) and pick-up time (some days they do an after school club so will stay later).
I lay out uniform the night before, and try to pack bags the night before too. When DS had packed lunches I made them the night before too.
Definitely deal with school letters as soon as you receive them, and note on your planner/calendar any dates you need to, e.g. events/meetings you need to attend, any non-uniform days, INSET days and days when they need to bring in a £1 for something. On the subject of £1 coins - I go to the bank a few times a year and get £30/40 in £1 coins. It’s surprising how often you need them between school and the tooth fairy!
Have a place at home where school bags live, and where school books (reading books, reading record and any spellings or homework books) live so you/your child can find them easily when it’s time to use them or to pack the bags.
My boys wear PE kit twice a week and uniform 3 days (DD it changes each term depending on what clubs she’s doing). For the boys, I have enough uniform and PE kit to have a fresh set each day (so 2 sets of PE kit and 3 of uniform). DD’s PE kit is fearfully expensive so I have less of it and have to be organised about washing it in time!