Hi... you will not get a ebay bucks code until sometime in October, you should get a email for the amount earned in the last 3-4 months period...when you get the email from ebay next month and you buy something within the 30 day period, sometime it don't auto add the code so you need at that time to enter the code manually for it to work.
You will get your eBay bucks certificate for eligible purchases made during the months of July, August and September on the Third of October. You can't spend your eBay bucks until then. Once you receive the certificate, you have 30 days to spend your eBay bucks or lose them.