Need to know where you live, what grass you want to have, are you willing to water every week in the summer heat, are you willing to fertilize?

No, weed and feed products are not what you want. If you want to kill weeds, fertilize first. Then, 2 weeks later, use a spray like weed-b-gone. If you have St Augustine, then you have to use a product containing atrazine. It is very hard to find until you find it. Seems like it does not come to the shelves until about May.

This is in houston, tx and yes I have/had st augustine

As you have seen the broadleaf weeds you have will smother out the St Augustine. There is an herbicide that will kill broadleaf weeds and is safe for StAugustine. The herbicide is atrazine and is, for the most part, off the market. Keep looking though. The last bottle I had was the Spectracide brand. It was black with purple labling. For your application you will not be spot spraying. Look for a bottle with the hose connector built in. I'm thinking I saw it at Wal-Mart last summer. For some reason it is harder to find in the spring.

Before you spray the weeds; however, you should fertilize. Now is a good time since spring is here and the grass is growing. Fertilize normally. Healthy weeds die better than unhealthy weeds. Two weeks after you fertilize, then spray.

Once the weeds are gone you can decide if you need more sod. St Augustine will spread about 10 feet in all directions every season. If you still have spots of good St Aug distributed around the lawn, you are probably home free. Be sure those spots are fertilized well. My preference is for organic fertilizer because you can use that safely all summer. Also be sure the grass does not die from drought stress. That does not require daily watering but it does require deep watering. If you restrict watering to monthly in the cool months (now) and increasing the frequency as needed up to once weekly in July, that's about right.

The last thing is to mow the St Aug at the highest setting on your mower. Tall St Aug is much easier to care for than short. Short St Aug needs more water and looks bad faster than when mowed tall.