A Wal-mart near me is selling live oaks (not sure for how long, hopefully it's still there when I get paid). They are in big pots and about 5-6 feet tall.

If I do get one, what kind of soil should I get for it?

I really don't want to mess this up as they are expensive for my budget!

Do oak trees grow naturally in your area? If so, you should be able to just plant it in your yard with 1 or 2 fertilizer spikes. You can pack some extra garden soil for good measure but its not necessary. Make sure you water your tree regularly to help it get established.

You could stir in a little bark mulch into soil, but little else. A dug hole in clay can create a bowl, crack the edges (and bottom) of your hole.

The addition of a little bark mulch in the hole, and a top dressing of mulch is to give earth worms a home. They will mine water exits your tree will need.

Plan on watering your tree at least weekly, for every week it does not rain. if this is a problem see a watering collar (in addition to mulch)

crazypetunias: Yeah, they grow naturally. Have two growing naturally by themselves. One is inside a crape myrtle and is a decade old based off it's height. The other was natural, too and much smaller. But I removed it and planted it elsewhere because it was at the front porch, but I don't think it's going to make it so I want a new one.

Coppice: I always wondered why people used mulch, I thought it was decoration. Thanks for telling me that. :)

Thank you both so much!

Mulch is also great for moderating soil temperature. With a couple inches of mulch, the roots don't get as hot in the middle of the summer, which results in less heat stress. It also prevents water loss through evaporation.

Make sure to mulch like a donut, and not a volcano! No mulch touching the trunk of the tree.

We learned the hard way that you should always as much as possible plant oaks in native soil.