I wish I had seen this in time. SEMA had a "Friday Experience" deal this year allowing the public to attend only on Friday. Price including SEMA Ignited was $60/ticket, and you had to buy it ahead of time (no on-site sales). Maybe keep an eye out for this next year, if they do it again.
To echo what everyone else has said, one day is not enough time to see everything! We went non-stop from gate opening to shutting down Ignite and even skipped lunch, and still saw only a small part of what was there. You definitely need to prioritize what you want to see based on the experience you want to have.
I think next year we're going to go the route of industry credentials so we have more time.