Do you already own a quality mask with a thermal lens? That should really be your first order of business, well before contemplating the purchase of your own gun. Second, most field rental guns (if not all) use crappy gravity fed loaders that cause jams and pinched and broken balls, severely limiting your fun. Do you know if the field you are going to play at uses CO2 or HPA (compressed air/nitrogen)? If they use CO2, I would take your $200 budget an buy a good mask, loader, an HPA tank.
If you spend wisely you might even be able to afford a secondhand marker in your budget - but even if you can't, putting a good loader and HPA tank onto a rental gun will put you leaps and bounds ahead of your co-workers running straight rentals, especially since you will be able to see through your mask and they'll have scratched up foggy rental goggles.
Here is an example of what I would suggest, but by all means do the research yourself.
$50 gets you a brand new high quality mask -
http://www.ansgear.com/Proto_Axis_Pro_Mask_Blue_p/protoaxispromaskblue.htm
If you buy new, expect to spend $80 or so on a good loader - but buying secondhand off of the buy/sell/trade forums at PB Nation or TechPB will save you a good chunk of money, as players often upgrade from perfectly good loaders to get the latest and greatest. Here is an example of what you should be looking for -
http://www.ansgear.com/Empire_Magna_Drive_Hopper_With_RF_Chip_Smoke_p/empiremagnaloadersmoke.htm
Same goes with HPA tanks - you can buy a new one from $45 or so up to several hundred dollars depending on the capacity, pressure, and material (aluminum, fiber wrapped aluminum, or carbon fiber), but you can often find a tank that is a couple of years old for much less than the cost of a new one... but, caveat emptor - paintball tanks require a pressure testing process called hydrotesting (hydro for short) every 3 or 5 years, depending on when the tank was manufactured and what it is made from. Fiber wrapped tanks also have a limited service life, IIRC 15 years. Don't make the mistake of buying someone else's problem (a tank that cannot be recertified or one that needs recertification before use). If you're not up to making sure you are getting what you
think you're getting, I would just buy an inexpensive new model, such as this one -
http://www.ansgear.com/PMI_Pure_Energy_Aluminum_48_3000_Basic_Tank_p/pmialu483kbasichp.htm
With all that out of the way, if you really want to buy your own gun, I cannot emphasize enough how important it is to actually read the documentation that comes with it - and if you buy secondhand, go to the manufacturer's website and download the manual. Many, if not all, of newbie paintball gun issues stem from improper care on the owner's part. If you want a recommendation for a gun (and I assume you do, since that's what you initially asked in the thread and I've TOTALLY derailed it) I'd suggest getting a marker like this -
http://www.ansgear.com/Azodin_Kaos_Paintball_Gun_Black_p/azodinkaosblack.htm This particular gun is simple, easy to maintain, and has nice features such as a low-rise feedneck and autococker threading for the barrel.
Hope this helps! Stay safe and have fun!