I've been through this c**p before, and I know how frustrating it is.
I changed the starter relay initially and that seemed to help temporarily, but it got to the point where it just wouldn't start even tho my battery was registering 12.8 (off). This went on for months and I almost killed the battery but trying to start it too much and I got all kinds of strange noises coming from my starter and stuff under there.
I then checked the voltage readings at starter button and it was about 11.4v. so I imagine it was even lower at the starter, too much resistance to power cleanly power the starter.
In the end, after checking conections, cleaning, tightening etc etc. I went ahead and installed a second relay coming directly from the battery and bypassing the ignition switch.
This was a miracle fix which i highly recommend. Honker sent me the link in one of my threads if you are interested in this.
I'm also no mechanic, but a little handy with things.
i hope this helps.