Wild camping is allowed most places but due to car drivers leaving rubbish it's not allowed near the road at Loch Lomond in summer.
Wishingwell Farmhouse campsite, Gartness and Drymen Farm campsite are both closed.(according to Google Maps)
Shops at Balmaha, Loch Lomond.
There are a few campsites besides Loch Lomond. Salachy Campsite is £5 which is the cheapest. But the campsite just before it is £7 and has much better facilities, including showers.
Rowchoish Bothy - good bothy worth using.
Doune Bothy - very poor condition, full of trash, don't use.
Beinglas Farm is a good campsite with a restaurant with food and beer.
At Tyndrum is a shop. Check the prices when buying, especially the fruit. Make sure you get a receipt.
There is a small shop at the Strathfillan Wigwams Campsite. I bought a snack there (but didn't stay).
There is a permitted wild camping on the north side of the bridge at the Bridge of Orchy but being near the road had noisy people. The Hotel has a restaurant and bar.
The route passes the Inveroran Hotel, food and beer. Wild camping.
Free camping at the Kingshouse Hotel. With beer and restaurant.
Kinlochleven - Has a good Coop Supermarket. I stayed at the Macdonald Hotel's camp site. Good and cheap.
Fort William - Has a large supermarket. Backstreet Hostel, good for town centre. Calluna Hostel - further away but a bit nicer.
Midges - get a midge head net. Creams will keep away a few. The burning coils keep away a few. But when there are lots (as there will be in July at sunset and sunrise) you'll need a head net.