You will hear that 50 acres is the "magic" number for Texas. In a sense, this is true.
The current laws in Texas restricting fire-on-your-own-land all exempt at 50 acres. But, most of those only apply in limited areas. One of which is in or immediately adjacent to a county with 500,000 residents. The other is within either city limits or RTJ for cities over 150,000 population.
That's really only about 25 Counties, and probably the same number of Cities in Texas--there are 252 Counties in Texas, you just have to be willing to live "rural."
If you can't live rural, then it get complicated. As alexander45 points out, you'd probably have to buy 100 acres in Colin County just to have 50 to shoot on. That's assuming uou could find 100 contiguous for under 8-9 grand an acrer (and more like 10-12). Denton County, ditto, except then you have a giant lake and three Water Authorities (and land prices closer to 15 grand).
If you wanted to look, check out east of Waco, towards Mart, Mt Calm or the like. Off to the east, down along a line from Paris to Crockett to Palestine there will be old farm and played-out timber acreage. Some of the area du north of Austin (but not on the I-35 corridor) will be good places to lock.
Probably some good places to look at along the break of the Edwards Plateau, but the land owners there buy and sell by the section,rather than the acre.
Get down between Boerne and Ft Stockton and San Angelo will be good areas to scout.
Yes, I've roughly outlines all the major geological zones/areas in Texas but the coast (and omitted the coast because it's expensive and heavily regulated).