well to answer your main question, yes, you CAN add a video card. hence why it even has a pci-e expansion slot in the first place. it will just run it at half the speed.
and just in general...that is just a terrible...TERRRIBLE motherboard. why would you want to buy this? seeing as you want to put in a graphics card, that seems to suggest that you want to do some gaming, yes?
i've got bad news for you. that motherboard just isn't gonna cut it. the sad reality is you have to spend a minimum of 95 dollars to get a decent board. i learned that through tons of research and asking a lot of questions.
but it looks like you're just going to have to live with it i guess. you don't seem to have an awful lot of money.
30 dollars will definitely NOT get you anything that will show a significant improvement. especially not with an 8x slot. i'm not sure if you can change what it runs at. perhaps a bios edit will fix that to a full 16x. but if i were you, i would try to spend at least 180 dollars.
that seems like a crap lot. but another sad realization i've come to is that if you want to game these days, you'll HAVE to shell out at least that much to get even a half decent card. that much will buy you one of two video cards. one is the radeon x1950. and the other is the ati radeon 3850. the 3850 is just under top of the line, and it offers decent performance. and it will fit that slot.
IF you can try to up your cash flow, and find the money for it, the only foreseeable upgrades you'll need to make in the future are a motherboard upgrade, a processor upgrade, and RAM upgrade. that's just about it.
if you buy a cheap piece of crap now, you'll wish you had waited and bought a better one.
not to mention if you go with really cheap now, you'll just end up having to spend more money sooner to upgrade to a better card. with how fast graphics are improving, any cheap piece of junk is going to be left in the dirt VERY quickly.
the only decent cards these days are the following:
geforce 7800
geforce 7900
geforce 8600
geforce 8800
radeon x1950
radeon HD 2900xt
radeon 3850
radeon 3870
the prices vary, so look around on newegg or tigerdirect.
i'd STRONGLY...STRONGLY suggest going with a card from the aforementioned list. because 1, you won't find a good graphics chip for 30 dollars. and 2, it won't improve your gaming experience. in fact, the 30 dollars cards maybe so outdated that they'll make it worse. that built in 6100 can do quite a bit.