Just thinking aloud here... If my budget were in that range and I was looking for truly noticeable gains, I'd concentrate on three or four things.
Gears - if you have a 2wd Ranger, all you need to upgrade is one axle. Look for a used axle with better gearing and swap it out. No need to pay a shop to change ring and pinion gearing, just swap the whole rig out.
Cam - Find a cam that lets you push the powerband up another 500 -1000 rpm. No more than that, or you'll hate life most of the time when you are just daily driving around town.
Exhaust - find a used set of headers that flow better than what you've got. This will be noticeable in combination with a good cam.
The big thing you could consider here is a nitrous oxide system. I don't normally like them, but if you do a reasonable shot (say, 50 hp) it's not going to cause world ending chaos to the motor and you could probably do it for years. Even a shot that small is something you WILL feel, and a lot more noticeably than any n/a modifications you could do.
Obviously a forced air system is going to generate more significant gains than anything else you could really do, but it doesn't sound like a supercharger is going to be an easy proposition for you.