2D game using sprites.

I am currently developing a 2D game in Free Unity. My problem is that I’m still not comfortable with modeling or animating in 3D.

My question is: Can i use 2D images as gameobjects instead of 3D objects? If particles and billboards can do this, why not do this with gameobjects, and such?

I know there are third party plugins for Unity that help with this, but i lack economical resources to afford such add-ons.

I’d be grateful if anyone could show some links to tutorials, or what should i have in mind while doing this (like things to increase performance, etc.)

I think this is the only option: