Hi Charley and welcome to the Forum
Exciting times ahead with Luna!
I would not recommend an extending lead as these can be quite dangerous and are not helpful in lead training a puppy. If you want Luna to have more freedom than on a short lead, use a long trailing line which you can catch hold of if she goes too far ahead. There are also many enclosed dog fields now which can be hired for 30 minutes for a dog to have free roaming in a safe environment. In the early days though I would only recommend letting her run free when she is in your home environment - garden space and concentrate on lead training with a short lead.
You can spend a fortune on dog toys and I know the temptation well! However puppies (and adult dogs) love all kinds of things that cost little or nothing to buy. Cardboard boxes, empty toilet rolls, empty flower pots, old socks etc. so don’t feel you have to spend a lot to give her fun things to interact with.
Chew items are a must. While puppies are going through teething they can be manic nipping and biting and you do need to have plenty of safe chew items to help the teething process and to divert them when they need to chew. Yak sticks when she is a little older; antlers; Anco Roots chews:
https://www.ancodistributors.co.uk/anco-roots
https://antlerchew.co.uk/?gclid=Cj0KCQi ... cPEALw_wcB
https://himalayan-chew.co.uk/collection ... 3067941025
There are more items on this link to give you an idea of some good chews although you may need to check the age at which they can be introduced:
https://www.jrpetproducts.com/search?ty ... IZEALw_wcB
The above are just a guide as there are other brands and many places where these can be purchased online or in shops.
A crate is important and it could be worthwhile also getting a playpen or room divider so that you can let Luna have rest time safely when you are not able to watch her without necessarily always putting her into the crate. An area with toys, chews and a bed for daytime resting can be very important as you cannot always be watching her and puppies are always going to get up to mischief if left to their own devices
She will need plenty of rest time when she first arrives in between play sessions.
Good luck and have fun. These early months with a puppy fly past and they are very special times