Biros or the Berol Handwriting fine at both my dcs schools.
Both needed Scientific Calculators from the start
If learning a language, then a French / German / Spanish to English dictionary is useful.
I'd wait and see with the gum shield / shin pads - in both my dcs' schools they rotate sports and only need things for a few weeks before they are on to the next sport
Wouldn't go for a ring binder - they are too bulky for their bags, but the plastic popper ones can be useful if you have a dd, my ds never grasped the concept of putting paper in his.
They will be given a 'Planner' to help organise themselves. Make Encourage them to get it out each day when they get home and it should say what homework is expected and what lessons they have for the next day.
Never needed any sticky back plastic for either of my dcs.
No problem with wearing a watch, but everyone under about 28 seems to just glance at their phone for the time, rather than a watch, so I wouldn't go and buy him one.
Find a way of sellotaping a £2 coin into the bottom of bag or inside a pocket somewhere for 'emergencies', and they will lose or forget their money.
Some school websites have things like diary dates and newslaetters on them - you won't get all letters that way, but it will help a bit.
HTH