My guess is if the patch doesn't stick you are doing something wrong.
I use a two dollar jar of elmer's rubber cement and those cheap patches from ebay you linked to. Always works fine for me, and I apply 1-2 dozen patches a year. The key is the surface prep and letting the glue dry completely. I am normally patching several tubes at a time so I prep the surfaces with sandpaper as someone else described, apply the cement and let them sit for a while. How long depends on how distracted I get doing other things. Could be 15 minutes, could be a few hours. The point is don't rush it. I have never needed to use a clamp or a stitcher. Right after I apply the patches, I inflate the tube and let it sit overnight to make sure the patch worked. In the morning I fold them up, wrap them in plastic wrap, write the size on the plastic with a sharpie and put them back in the spare tube bin.
I also have a jar of rema cement and a box rema patches. They work too.