Texas is a big state so depending on where you are in Texas and exactly where you are going the distances might vary a lot. I am guessing that your tour could be anywhere from 700-3000 miles based on that description. Can you narrow that down a bit? Also will you be cooking and camping, credit card touring, something else? That and what kind of daily mileage will you do?

In any case $5k is probably enough for even a credit card tour for any of those distances. It would be for me any way.