I have a similar diaphragm compressor to the one shown at Harbor Freight. I've heard that you should make your airline as long as is practical with this type, and pulsations will have less of an effect. The long airline then acts like a tank or buffer. So I've always gone with that. But there is a downside: the longer line wants to allow condensation to build in the line as the compressed air cools. This is one good reason for a tank/trap setup.
Without a tank, back pressure is also an issue. Badger recommends adding a tiny shunt hole in the compressor head hose fitting on tankless set-ups, to prevent back pressure build-up. I added a foot switch on my compressor, as well. That way, when I wont be spraying for a length of time, I can switch off the motor.
If you're handy, you can add a small buffer tank like I mentioned with the unit at at work. I plan to duplicate that with 4" PVC pipe on my compressor. Or maybe you can use one of those reserve tanks used for inflating spare tires. Even a used propane cylinder could work, I suppose - almost anything that can withstand the pressure should function. With one of those small pumps used for emergency tire inflating you just may be in business.
When it comes to tools, the words "cheapass" and "quality" do not normally go together. Oh, you can luck out and get used tools that are right for the job... I did and got my compressor for $5. So, they're worth looking around for. But, no matter how you cut it, you're probably going to be in for at least $50.