Need advice about grass seed planting in middle of July. Any advice?

We rented a beautiful home except for the weed yard. After 3 yrs of trying to pull, finally we sprayed and killed them. We have a sea of hay. For the previous yrs I made big areas, mulched, mulched, mulched areas and planted flowers, birdbath area w small bushes, etc. It's a lot better but don't know what to do next. We have centipede grass (it's FL afterall). I'm saw a bag of centered seed for $60. That's expensive if it doesn't work especially putting $$ in plants and mulch. So does anyone know if grass seed works. Or what else can successively be done? Anyone an expert in grass seed planting in middle of July? Any help would help us. Thanks for reading this.