how much per day if i want to hire a car and drive myself from Chengdu to Jiuzhaigou?

Hi, the car rental fee for the journey per day may be about CNY 1,000 or more.
Absolutely you can get a hotel on the way. Don't worry about the accommodations.
Dear Oct. ? Well, actually, it will be during autumn and the scenery in JZG then is enjoyable.
Comparatively, it can be cheaper by air than renting a car from Chengdu to the scenic area. As for the ticket promotion, you can certainly get it. It is hard to tell you an exact price, so I suggest you refer to the website:
https://www.travelchinaguide.com/china-flights/

Owh. thanks for the reply.

in Jiuzhaigou, is there any train service? train to Lhasa, tibet?

Hi, no train runs to Lhasa from JZG. I suggest you go to Chengdu to take a train to your destination. But only one train is in operation from Chengdu to Lhasa - T22/T23, taking about 33h for the whole journey.
Due to the time-consuming journey, you may also choose to catch a flight, which takes about 2h or 2h and a quater from Chengdu to Lhasa.