The key question: what resolution laptop do you want? If you're planning on getting a 1080p laptop, the price range is going to be much higher for gaming than a 1366x768 (or similar) laptop, because you can get away without a discrete GPU for casual gaming at the lower resolution, but not really at 1080p.
-edit- I'm thinking primarily of AMD's Trinity APU as the thing to drive a budget gaming laptop. If you are dead set on a core i5 setup, you'll have to pay more and will need a discrete GPU. Also, you're not going to be doing any meaningful overclocking (and probably none at all) on a laptop.
Nobody but you can really answer your question but I can help you start looking in the right place, then you really need to research all your options, if you have lots of money you can just go buy the best and forget, but that isnt usually case for most of us.
I assume from reading your post you haven't bought a laptop yet, here are two options that will give you what you need (just copy and paste the links to your address bar if their not active links.)
This is a Sony VIAO, its pretty afforadable, but mostly it has the option to get a NVIDIA GeForce 640M graphics card. this is a good mid level card should do most of what you want at a decent price, but remember its an option it makes this $640 laptop a $740 laptop, and if your willing to spend a little more you can get this....