Are you hoping the $300 laptop would run Leadwerks? I would be shocked if a $300 laptop would run Leadwerks. I think you'd be better off getting a tower PC so that you can upgrade it later and put in new gfx cards over time, which is what really matters with any game/game engine. Laptop gfx cards seem to be hit and miss and just bad in general. I guess for me the ability to upgrade components is far greater than portability for my game dev machine.
Something to note, right now Leadwerks doesn't need a high end gfx cards, but I still see people with laptops (maybe older) complaining it won't run Leadwerks. However, when the deferred renderer in introduced to Leadwerks it'll need good gfx card.