How early should I get to the event in order to be able to park in the parking lot and how much does it cost

There are about 120 parking spaces in lot on site. Gage the show interest accordingly. Not sure about cost when there is a show... the remaining entrance gate is left open all the time becasue it is broken and they recently removed and paved over what was left of the exit gate to allow for a wider exit out of the lot (and get rid of potential liability for cut off stubs of sharp old metal guard rail posts that were covered over with cones)

I park off site too. But we drove by the area one day of an event and the lot was full easily an hour before the show, it looked like a small lot

Not sure about parking, I park off site