some of us manage to not get tickets, but being from PA helps(points don't transfer holla!) Like Chris said the gas is easy to figure out, but you should figure out your average highway MPGs while driving mildly/aggressively plus add some change to the cost/gallon as some places are more expensive.
Then factor in how much you drink, if you plan on going to a strip club, if you want hookers(

) and how much crap you plan to buy along the way. It's nearly impossible for me to resist drinks and beef jerky when we stop for gas, along with funny stuff like hats and other local novelty items.
I usually do the rally plus drive out the scenic way so its about 6500ish miles which (6500/200)*3.5=$1137 in gas, 4-6 shared hotel rooms on the way out, cash for any casinos we happen to stay near,40ish per drinking night(depends on where and how much though), $40 a day on random junk and you've got the guesstimate:-p