For $500, look at the 2000 PSI fill Maximus with hand pump. If you want to go really cheap on the pump, look at eBay, some Chinese cheapies going for under $60 and the reviews I've seen were OK. Reviews are good, though the trigger isn't the best.
There's a new Crossman called the Fortitude, though I have no idea what it is like. It's a 3000 PSI fill, so you can fill it with a pump, but since it's a small air cylinder, should be easier than something like a Marauder.
Air will be the Achilles Heel on an inexpensive setup. I would buy a Maximus before I'd buy another spring gun though.
On paper, the Fortitude has some really good specs,
Small air cylinder, but regulated so gets lots of shots. They claim 90 shots per fill. You will be limited to whatever pellet Crosman used to set the regulator, but it's a heck of a start. It is magazine fed, ready for optics and comes in at $300 or so for the gun, then add a pump and optics.
The Maximus can be had on the Crosman site for $220, then use the AGNATION discount code for a 25% discount means it's $165 and free shipping on Fridays. That's a darned cheap PCP, and leaves lots for upgrades.