Luggage and bags:
I live here, we have a saying, If you don't like the weather in Texas wait 5 minutes. It Varies alot... if you are coming in summer it could be anywhere from very rainy to comfortable to blisteringly hot (literally). Pack sturdy, comfortable clothes like blue jeans and shorts. Boots if you have them and sneakers and T-shirts oh, and at least one jacket or raincoat. In the City it is possible to stay out of the weather if you work at it so bring what you want. If you are coming to shop, be prepared to look good. If you've come to party, this is probably also a good idea... as it is pretty much everywhere else. :)
Clothing/Shoes/Weather Gear: I have a coat. I wear it sometimes, when I'm in Boston and Scotland and other places. When I'm here, I tend to carry it around in my car in case I need it for anything.... a light jacket in the event of a blue norther (big honking wet rain storm whips off th Colorado mountains, hooks left and makes a bee line for North Texas, temp drops about 20 to 30 degrees in a couple of hours) rolls through is probably a lot more practical. Other than that, please remember that most people can still sunburn right through a white t-shirt.
Toiletries and Medical Supplies: LOTS AND LOTS OF SUNSCREEN, and a bottle of water never hurts. I like the stuff that is sunscreen and bug repellent all in one. Never know when the skeeters, or the chiggers are gonna try to get you. And don't even get me started on those freaking fire ants...
Photo Equipment: Do what you feel we have great light. Lots and lots and lots of great, great light. :)
Camping/Beach/Outdoor Gear: Larger tent is better for summer, doesn't get as hot. Other than that use your common sense. It is against the law in Texas to burn ground wood in any state park so bring your own wood or coal.
Miscellaneous: No matter how tempting, always have shoes. Sunshine makes blacktops melt a little and it's repulsive to have to scrape tar off the soles of your feet. Mind you I haven't had to do it for about 20 years, but that's just because I've learned my lesson... and I really like shoes...