If not overclocking or in a hot room (over 80F) the stock cooler works just fine for heavy gaming. It will require a good case-going old or too cheap here will hurt big time.
An 8350 will not have computational errors till 68C+(depending on system quality and settings), thermal shutdown is over 80C. If you are only getting 50 while gaming, you are either in a non CPU intensive game, or are looking at the wrong place to determine the temp. Don't use the per core temps-they are almost always wrong. HWMonitor (or Hardware Monitor) by CPUID is what a lot of review sites use for CPU temps. Use the CPU temp under the motherboard section. This program is free (I found it on Cnet)
Go find Prime95, run the max temp test (middle option) for half an hour, and if you don't have errors then your stock cooler is more than sufficient for your case, and unless you plan to overclock DO NOT NEED TO BUY ONE. Prime95 forces it to 100% load for everyone-apples to apples-it is also free. expected temp range on 8350/stock cooler with good case @ 71F/21F: idle-27 to 30C, prime95 100% load for 30 minutes- about 64C. I used a CM HAF XB case with all fans installed for those numbers.
Don't go by a gaming temp: that is utterly useless. Tomb Raider will only get me to 39C (I have a 8350/stock cooler) and the Sims3 gets up to 51C, GTA4: 55C. 35C while gaming is going to be unrealistic for many games-and not for 20-30 euros. Small self contained water cooling options are available for about 60USD. Water cooling options got much better and less of a hassle in the last few years, so you may find something even better for less.