I've been using Bayer Ultra, its like $12 a bag at Home Depot and it deals with fireants very well.
Also, if you want to go organic, Dried Molasses works very well also. The ants don't like the smell, and You feed the microbes in the soil that kill ants.
Although 5 years ago Dried Molasses and other organics were much much cheaper than they are today, they still work well jumpstarting your lawn. I've been spreading a 50lb bag of dried Molasses along with a 50lb bag of Soy meal (insoluble protein is like 50% of the volume), and they are incredible at adding more organic matter to your soil and chasing away bad insects.
Easy way = chemicals
Hard way but better for your garden and plants = organic