You can get a great finish spraying with a
Preval sprayer so that isn't what your money is buying. I have used just about every type of gun at every quality level there is and here is what I have found out.
The cheaper guns almost always have some kind of crappy "O" rings that keep them from leaking and always seem to swell up making the gun useless, this usually happens during the cleaning process especially if you are soaking the gun.
Just running solvent through a gun doesn't clean it properly. Even gun cleaning machines that pump solvent through the fluid passages don't do a decent enough job. I have used them and then taken the gun apart, I always find some residue inside the fluid tip and fluid passages which will build up and potentially ruin your gun.
I own a Sata gravity gun which I got from an automotive painter friend for $100, It is an older NR95 model which still works great. The difference in this gun is that all metal parts are machined and there are NO O" rings to go bad. (A new Sata can run over $800 so they are not for everyone)
I would buy a gun from a reputable supplier (Binks, DeVilbiss, Sata, Iwata etc) and then if required get all replacement "O" rings and gaskets needed so they can be replaced.
Become familiar with the exploded diagram of your gun and dis-assemble all fluid related parts after each use and clean in required solvent, after using water, a flush with acetone is a really good idea to keep any aluminum from pitting. NEVER soak a gun completely in solvent of any kind! The air passages are not intended to have fluids inside them and can cause scaling where it can't be cleaned out resulting in chunks of grit coming out in your spray pattern.
The proper way to dis-assemble a spray gun is to first remove the fluid needle, this is very important or you can get leaks from the lapped fit with the fluid nozzle. After removing the fluid needle take off the air cap and then use the proper wrench to remove the fluid tip. (Don't be tempted to use your vice grips or pliers!) Remove any teflon or rubber packings or O rings and make sure you don't soak them in solvent. Using a proper
gun cleaning kit, thoroughly clean all fluid areas of the gun and soak the fluid needle, fluid tip and air cap in clean solvent. Check inside the fluid nozzle and make sure no paint is still inside, the small bottle brush in your gun cleaning kit is excellent for this.
Re-assemble your spray gun making sure to replace the fluid tip and properly tighten it before replacing the fluid needle assembly. Now the next time you need it your gun will work perfectly just like it did when it was new.