Basically copy coupon, view price history or create e-mail price alert. Do you want to know what the best price is?
Octa Core, CPU Qualcomm Snapdragon 653, Resolution 1440x 2560 pixels FHD+, GPU Adreno 640, ROM 64GB, 4180mAh(Built in Polymer Battery), RAM 4GB, OS Android 7.1.1, Display Size 6.0 Inch Conring Gorilla 4 Glass
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. You can get coupon down below.
Link: Banggood product page
1. ($112.99): Email5
put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BG5F9
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Here is price history (for all/most countries) for YU FLY F9 4/64GB.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).