It's really whatever you want, nobody cares.
We've never defined what a gambler car actually is, rules are for dweebs. The original Gambler (2022 Gambler 500) intent was around $500 but that was only to serve to set the tone and make sure everyone was in sh*tboxes. There was also a general guideline that if you spent more money it had to be worse than a cheaper car (ie Fiat, Citroen, Yugo etc.). You could spend whatever you want after, spraypaint, stickers and KC Daylighters don't make anything faster or more reliable, huge lifts and tires really only make cars slower on the simple backroads we travel and they usually break quicker. Also it's funny if you bring out something nice and beat it up, conversely it's mostly just gravel and dirt roads, "to Gamble is not to destroy". In fact I think more cars get saved by gambler than are ruined by gambler...
Some year one cars^
Most of the original cars were barely modified at all, maybe some stickers and spray paint. Gambler is a war of attrition and stockish cars usually do better, just bring TWO spare tires. Some people keep their cars year after year, for some the building is most fun.
There are no parameters to cheat at something that's all about fun and adventure. Build what you want, build that crazy thing you never had a reason too until now. Bring out that classic 4x4 and work it's legs (Rattlebomb Rally).
Late model cars and 4x4s are welcome (SIRCH&RASCUE) as well, having reliable and capable stuff around the events is usually a good idea.