If you play Texas Holdem, the Choctaw Casino in Durant, OK is the closest to Dallas. It's straight up U.S. Hwy. 75 to Durant. Plus, the hotel, casino and other amenities are a lot newer. Easy access to the casino and plenty of parking. Winstar is an older casino with limited gaming.
If you go east on I-20, it is about 170 miles to any casinos. Shreveport, La., and Bossier City, La. are across the river from each other. There are only two casinos that play Holdem -- El Dorado and Horseshoe. Best buffet is at Horseshoe.
Good Luck!