Convert static joomla template to responsive?

Can someone give me an advice, what is best and easiest method to convert static Joomla 2.5 website to responsive website.
I tried media queries with 3 different css but I am not satisfied. I just don't know what to do with sidebar... it looks realy stupid on mobile devices.
Another problem makes me K2 wich is installed on that website.
Is there any way to put all content in some grid layout and make it fluid or...

Thanks