Inevitably there will be some things that need to be stored in the garage. Move it all into one corner. Hang what can be hung and stack everything else. Conceal the "junk" with some long drapes bought cheaply at a thrift store, or use large corrugated cardboard boxes to construct a wall around the junk. Decorate the drapes or cardboard "wall" with posters, ribbons, bows, drawings, paintings -- whatever suits your fancy.
Scout around the local thrift stores for some rugs or carpets you can get cheaply. Scout around your neighbourhood to see if any neighbours have recently replaced carpet. Somehow you have to cover that concrete garage floor to make a comfortable space for yourself.
Scrounge, ask friends and relatives if they have extra furniture, lamps, tables, cushions, etc.
Have fun setting up your space.
I've recently decided to move into my parents garage to have my own space until I turn 18. I don't have much money and there's a lot of stuff in there to make my own, like old tires, car parts, ladders and broken furniture. I just need a few ideas to DIY. Any suggestions would be very helpful. Thanks!