Make sure all motherboard drivers are the last ones issued for that motherboard, the ones supplied by the driver disc are so far out of compliance with windows 10, you'll have issues.
R9 280 generally requires a decent 550w psu, that 500w is skimping it a bit, having a locked cpu helps keep demands down.
There's several things going against you.
I5. Can have issues in some games that are optimized for 8 thread usage. You have 4, so expect high cpu usage and some loss of fps.
R9 280 is a mid-range ability gpu, can struggle on some newer games intense graphics, you'll need to knock back the detail settings a bit.
1x8Gb of ram. 1 stick means single channel, that's @20% loss in performance vrs dual channel (2x4Gb) which can be telling in some games that make use of higher bandwidth availability. Adding a second 8Gb stick will help, maybe not in size, you really have no need for 16Gb, but the dual channel setup will increase ability.
SSD. You don't have one so everything is regulated to HDD speeds, which will hurt online gaming, especially head to head stuff, PvP, higher drop servers etc. Load times simply take too long on everything even your toons gun has to be searched from files on the HDD whenever it comes into the picture. Every time.
What you have is an OK budget build. Because of platform changes, the only thing I'd suggest is trying to get ahold of a used i7-4790k, it's a plug-n-play cpu on that board, offers much better power and speeds even at stock than the 4460,and it's an i7 vrs the i5, so has the benefit of 8 threads ability.
Get an SSD as a boot drive, keep games on the hdd, but your saved games on the SSD.
Of course your other option would be to replace the platform, go with Ryzen 1500x or 1600, B350 mobo and at least 8Gb (2x4Gb) of fast DDR4 ram (3000/3200), OC to @3.8GHz. That'll come in somewhere right about $400, just don't tell Mom's friend.