There isn't direct flight from Malaysia to Jiuzhaigou, you will have to fly to Beijing Capital Airport(https://www.travelchinaguide.com/cityguides/beijing/capital-airport.htm) first, and then take a train or a flight to Chengdu, from where take a plane to Jiuzhaigou. It's hard to say which airline is cheap, it all depends on the booking status. You may check China flights(https://www.travelchinaguide.com/china-flights/) to get the flight schedule and ticket prices.

Mark is incorrect in his advice. You can fly direct from Kuala lumpur to chengdu on air asia and then use internal flights from chengdu to jiuzaigou. I am sure this will be a lot cheaper than mark advice!!!