karandeep :
Around 30 to 60 fps
And let me know of a budget but decent graphics card and what kind of psu should I use
Is it possible that the card could be around for 100 dollars or so
So here's couple of options for you:
1. GT 720, those cards go for around $30-$40, you will not need a PSU upgrade and you will be able to play GTA V at medium settings between 40-50 fps at 720p, I'm not sure about 1080p, maybe you would be able to play at 1080p with low to medium settings at 30-40 fps.
2. Get a PSU upgrade and get a GTX 750Ti, the GTX 750Ti costs around $130 which is a bit more than your budget that you should be easily play GTA V at 1080p at around 50fps. The tricky part is, there is no PSU upgrades for hp compaq 8300 elite small factor, to be able to upgrade your PSU, you need a converted cable, and there's only 1 guy that makes then and sells them on ebay, but he ended the listing on 21st Dec 2016. He said he will be making more, so I would keep an eye on him, here's the listing:
http/www.ebay.co.uk/itm/112242829603
And here's the videom from that guy:
https/www.youtube.com/watch?v=0VCslFs6lW0
He said in the comments a week ago that he will be making more. If you want, you could PM him on YouTube or Ebay and ask him when he will be selling more. If you don't want to wait, you could get the Nvidia GT 720 that dosen't need the PSU upgrade but I can't gurantee that you will be able to play GTA V 30-60 fps at 1080p, you will be able at 720p.
EDIT: Also forgot to mention, some HP computers have a lock in BIOS that blocks any GPU upgrades to prevent people putting in GPU's not designed for the computers and then break the and ask for a replacement or refund.