We bought as we go along.
The uniform was the biggest expense and we bought it from the school in the summer. And PE kit from the school too.
Shoes and socks, tights etc. bought during summer.
We had dictionaries and thesaurus at home, didn't spend money on them initially however after the school started and we found out which books they are using, we bought the textbooks for Science and the books plus cds for foreign languages from the school.
In our school all school purchases, books-dinners-school trips etc are via an online payment system called Tucasi. Your school might be using them, it's great convenience.
Food and nutrition (cooking) supplies were approx 30 pounds for the year. Paid to school in September via Tucasi.
Topped up dinner money on Tucasi. There is a daily cap you set for your child and they can't spend more than that amount daily. Top up online as and when needed.
Scientific calculator, maths set and pencil case etc again we bought them in summer. Also bought various stationery, notepads etc. After we bought the maths set and the calculator in the summer, we noticed that the school sells them very slightly cheaper too. It's good to know if existing ones get lost or damaged, it would be easy to replace from the school office.
Laptop is a big expense if there isn't one already.
Mobile phone: some kids have quite decent ones but some are happily use more basic, old leftovers, at least in year 7. Dd got a very cheap and basic one at first as PAYG but then upgraded to my old (still quite basic) android phone with internet connection.
Also, we live in London and we made sure we got an Oyster travelcard issued and made sure to do several trial school runs by public transport in summer. I realise it's not an issue for you. Secondary school is the first time dd went to school alone, as we used to do the school run by car in primary.
School trips are very expensive compared to the primary. They have smallish day trips to a nearby places, for geography or history, which costs around 20 to 30 pounds. Not compulsory to send your child.
There is PGL type residential trip within the UK, costing hundreds. Not compulsory. Usually takes place in June- July months.
Also there are other PGL type holidays abroad which costs an arm and a leg. More than the cost of a package holiday for a couple! And it takes place in the summer holiday when schools are closed.
Also Skiing trip to the USA in either winter half term or christmas break, i can't remember which, and we will not be sending dd. It costs nearly 2000 pounds which is absolute madness!
Foreign language day trip to Germany or France or wherever, again not compulsory to send your child. Usually takes place in summer term. If it involves Eurostar, it will be expensive. All these trips are good but many kids don't join them. Mostly they do the local area geography day trip and maybe UK based PGL residential too.
Schools do theatre trip etc which could be subsidised heavily and might cost little.
Our school arranges extra curricular activities such as music lessons, sports coaching with extra costs but i don't know the going rate as we don't utilise them. For that reason i wouldn't know the additional cost of special sports gear and equipment either. My dd does some specific sports outside the school, her school doesn't offer those sports.
You asked apron, lab coat, protective eyewear etc. We didn't need to purchase those. School provided them.
Our school does lots of lunchtime and after school clubs, appealing to variety if interests. I'm sure your DD will find something she likes too.