It will not be possible to build a new gaming system for 300 RON. You will need at least the following:
Motherboard
RAM 8GB
SSD 120GB +
Graphics Card
Power supply
I'm assuming you already have a monitor, keyboard and mouse and you will be using a free operating system, e.g. linux.
The cheapest SSD 120GB on dc-shop.ro is:
http://www.dc-shop.ro/ssd_uri/ssd-silicon-power-s60-120gb-sata3-2.5-inch-l/
This costs 199 RON
There is no way you can buy the folowing for 101 RON
Motherboard
RAM 8GB
Graphics Card
Power supply
This site is great when building rigs : pcpartpicker.com
edit
It's been suggested that maybe you are just looking for an SSD drive with a budget of 300 RON.
If that is the case then I would recommend spending a bit more and getting a 240GB SSD drive. 353 RON
http://www.dc-shop.ro/ssd_uri/ssd-patriot-blast-series-240gb-sata3-2.5-inch-l/
http://www.tweaktown.com/reviews/6918/patriot-blaze-240gb-ssd-review/index10.html
To me anything less than 200GB in an SSD is a false economoy. If you absolutely cannot spend more than 300 RON.
http://www.dc-shop.ro/ssd_uri/ssd-corsair-force-series-ls-120gb-sata-3-2.5-inch-mlc-l/
Has the best read/ write speeds. 291 RON
However, when gaming the graphics card will largely determine the frame rate and not the SSD.