Im buying some property that was an small dirt pit. It is now mostly red dirt where i'll be building my house and all the topsoil is gone. Currently there are some small pine trees and very little grass. I assume the PH is terrible, (will be getting a soil test done soon). What will I need to do to get some decent grass growing and potentially some trees in the future? Bringing in topsoil for my actual yard will definitely happen. But as far as the rest of the 9 acres, is there a rye or some other grass that will grow and potentially build up the soil?

One of the best soybean crops I've ever seen was in a red-clay field near Troy.

I’d keep digging and make one huge dirt out. There’s a lot of money in dirt

Do some research on reclaiming strip mined land. Hunted some in Tuscaloosa County for several years that had been reclaimed and it had made a good come back in supporting wildlife.

Throw n mow...

Red clay on our lease has decent ph and grows food plots ok but 90% of the time It's too wet or too dry to till. The pine trees grow a lot slower in red clay than in sandy soil. Every one our plots with red soil are high in phosphorous and grow clover very well

Kudzu will grow good there!
Seriously though, pines should do ok for you there. I’ve got some spots on my property that are similar to what you have but due to erosion. Pines were volunteering there when I bought the place. I just let them have it. It’s been 20 years or so now but the land under them is either thick pine needles and clean or grassy depending on how thick the pine trees are.

Try longleaf pine. It seems like the worse the soil is the better it does. It doesn't do well in good soil ( at least not on my place) because the competition outgrows it if you don't tend to it a good bit.

I have always seen long leaf pines on sandy and well drained sites

I should have been more specific to my wants for the property, I don't want any pines, id like a more mixture of hardwoods and some fruit trees in the future. Not for any timer harvesting. Just a variety on the property.

Grows well on it for sure.Grows well on the side of mountains too. They have such a slow upstart that good soil areas have too much competition for them.

Get some cereal rye and clover down this fall just to have something growing.