buy cheap games and shop them, trade them off or sell them. eventually trade up to the pinball machine you want. there are many ways to build a collection over the years. i used to buy only nib games, then i started giving older games a try. right now my favorite is smdm in a row of cv, woz, ss, mb, space station, nba fb, bk.
was looking to buy nib again (gotg) by selling one off but am holding off on this.