Sport kit- how many to buy?

It depends on what they're expected to wear/will they be going out in all weathers?
Dc1&2 have shorts and tshirt all year and a jumper and a skin layer for colder days. Dc3 has skin layer, shorts and tshirt, joggers and jumper, raincoat (has health issues and gets cold quickly). Also how often is pe? we managed with one set of everything and dc are old enough to bring it home when needed, in yr7-9 that was weekly as have twice weekly pe, in y10/11 they only have fortnightly pe so it usually comes home monthly unless had a muddy lesson.

How often do you do a load of washing?
Do you have a tumble dryer?
How sporty is your child (so are they likely to do after school clubs involving sport)?
How forgetful if your child?
Is it generic kit or branded?

DS goes to school and wears it all day twice a week and then does after school clubs on the other three so actually wears sports kit every day of the week. He's generally quite organised but, if he takes his jumper off in the middle of games or training, he just chucks it to the side and often forgets to pick it up. Then it takes a few weeks to get to lost property.
We ended up with two of everything and an extra jumper. Otherwise, I was having to do every night, something I often do anyway but it's nice not always thinking I have to.

How often is he doing PE a week? Is it worn any other times too?