Sure. if you start in august, you will be growing mostly fall greens, and those are
a) the most nutritious of all veggies and b) in most cases you can let them go to seed and collect seeds for future crops
Yes, staggered seeding for plants with a short harvest season (such as lettuce), but maybe only two or three plantings for longer harvest veggies such as zucchini or chard. Get a chart with planting and harvesting times for your area, and pick only what you can eat. In Dallas, you can have winter greens throughout the winter, no problem. Just make sure everything is in the ground by october.
Use all of your kitchen scraps, all of your leaves, and all of your grass clippings as fertilizer and mulch. In a place like Dallas, mulching should save you a lot of water money. If you have already established plants, consider five or six inches of mulch around them.
If you start this august, and the soil is more or less prepared, I suggest (tomatoes will be for next spring):
1) soil test at your local extension service 2) start with relatively easy veggies such as lettuce, chard, collard, or various salad greens (it will be difficult to mulch greens, except relatively large plants such as collard or chard... direct seed the rest, if the plants are thick enough they will mulch themselves some). As the weather grows cooler (october) you can try planting some arugula or other mustards. 3) get a herb patch going as it gives a lot for little effort. I would start with oregano, thyme and sage, perhaps rosemary, given the zone.