Thinking About Upgrading

recently i watched Logans build a lower end gaming pc video and im thinking about upgrading one of my computers cause i noticed my specs are similar to the one he posted but im not sure which is the best way of upgradeing. my budget is about $300 and my pc specs are an

 amd a8-5500 quadcore 3.2 GHz (3.7  turbo),
8gb of ddr3 system memory,
1tb 7200 rpm HDD,
amd readeon HD 7560D (apart of the apu),
and only a weak 300wat power supply, and 

my mobo only has one pci express slot thats 3x 16 so i can only put in one modern gpu in it. What would be the best rout to go to upgrade this so it can handle newer games at decent resolutions and decent settings with about 30 fps (decent being med/high at 1080p) at under $300- $350 (if its even possible). 

sorry if theres alot of other post asking this but i couldnt see any in the pages that i checked. thanks in advance to any who reply to this 

GPU - 7870xt - $254

PSU - Silverstone Strider Essential 600W - $60

As long as you are comfortable enough in doing this yourself you'll have a nice little gaming rig. Not sure what your case is so just check that you can in fact fit a full size atx psu and a reasonable size gpu in there. Then just address airflow as needed to keep temps in order.

 

i recently checked the measurements in the case and it was able to fit a gtx 660 in there with room to spare and looks like enough room for cable management  so i should have enough room thanks for the quick reply.