I bought a used 93 ford ranger and the guy who sold it did a ,ot off the repairs himself halfass. the brakes feel spongy thru the first half of the pedal. and the brakes arent very poweful. the kid said he just did the rear drums. and they make a big clunk inn the rear if i step hard on them. i checked the rear bleed and their is plenty of pressure.

I'd check for proper shoes & placement first, Primary (shorter lining )in front, secondary (longer lining) at rear.
Then check for any grease/oil on shoes, or seal leaking on to drum. From there, check adjustment, to make sure not too tight, as well as self adjusters moving as they should, and installed properly. Might be smart to check for proper width as well as proper fit to drum. Check emergency cables aren't too tight as well. Then I'd look at front brakes for seized or partially seized calipers. If the fronts aren't working as they should, that fluid pressure has to go somewhere, and if front are seized, it will increase to rears.

First, dont buy any car from some DIY yahoo thats too cheap to pay for brakes, that can get you killed. About the rear clunk, theres a problem so take the drums off, and the problem should be obvious. you may need a hardware kit and a picture of what the brake shoes are supposed to look like properly mounted