Ah geez, we have been infiltrated by a Californian...I am out
Grab a chair and get some mud boots because the
gets deep. A lot of good folks and a lot of good information here.
Gun: get one that you can shoot well. .243 will get the job done, but if I only had one (if the government ask, I only have a pellet gun), I would go with a .270 or 30-06. Both very versatile and you can hunt pretty much any animal in Texas with one.
As far as gear, get what you want. Part of the fun is realize that you can do without 99% of it. Texas hunting varies, so get a T-shirt, some thermals and a jacket.
Stick around bud, you can probably find a few folks that can help you along. Advice is free, but worth what you paid.
Might consider a few guided hunts to get your feet wet too