Are people really suggesting PHP is all you need? LOL. Have a look at one of the available gambling sites out now, Bustabit. PHP is just a drop in the bucket when it comes to Bustabit. You need to learn javascript, web sockets, html, css, php, sql, etc. A shit ton of languages. Then comes the bankrolling part of everything. To run a decent gambling site you will need around 400+ BTC. I don't care what anybody else says, you need a HUGE amount of money to even think about starting a casino. Then comes the $10k that you should use as a start up for a bug bounty search. You need people to find bugs in your site so that they aren't abused later down the track. Just look at what happened to Primedice a shit ton of times. They have lost thousands/millions of dollars to cryptography related issues in their site, related to server seeds and stuff. But something tells me that you (op) don't even have $5k to start a site with.
What happens next? The legalty issues.
http://www.bitcoingg.com/bitcoin-gambling-legal/ If you've ever been on PrimeDice on a VPN, you'll see that half the countries are restricted due to gambling restrictions in the residential area. That's a huge problem in most authentic gambling sites these days, and you could get into a bit of trouble if you are not complying with the laws.
If you are indeed on a restricted budget (let's say 5 BTC) then you could buy a site script for 3 BTC, and then hire a developer for 1 BTC to connect the script to the moneypot API so you can use their bankroll to fund your site. Although the profit from that is quite low, it's better than nothing and it gives you a bit of a reputation boost at start(?). Then you can keep the rest of your BTC in reserve as an emergency settlement type of thing.
Good luck, feel free to ask if you need more help.