Transparent Images as UI

Hello,

I'm trying to make a space game with futuristic interfaces in-game (not main menu, not pause) which means game will be controlled with mouse and everything from minimap to inventory will be my custom designed in-game interface.

Right now i'm working on click to move and drop a png mark there. From what i've researched, it's done by using that png onto a plane as a transparent texture. Even though it works, my camera does not recognise it, also the quality is so bad and i can't scale my plane as my png's pixel size.

How can i work with this in a better flow? Would NGUI help me?

Thanks, Met.