I've actually used some existing CSGO gambling sites and would be very excited to create this product for you.
I am one man capable of doing the whole job in one month, working daily full time for you. I am very qualified in all the skills you listed (PHP, HTML, etc), and have lots of experience building entire web products working alone.
I am new to Freelancer but not to professional web development. You can see code I've written in my spare time, some of which is quite popular, on my GitHub profile github [dot] com/bramgg
If you work with me, you are working with someone who understands your product, communicates well, and has years of professional experience as a senior developer. Because I am new to Freelancer I am willing to start working with no upfront payment and can keep you constantly updated on development.