I think you're missing the point of the upgrade here. He's indicating for something towards gaming, the SSD will only increase load times of the games, nothing else, thus no use for it with this limited budget.The hdd is the bottleneck of your setup. Maybe invest in a ssd. Won't help your gaming though.
hereticangel and NomNom's advice on the upgrade is what you should follow. Start with GPU upgrade HD7870 will be fine (with the games) R2k.
PSU ~R700:
http://www.wootware.co.za/coolermaster-rs550-acaae3-gx-550w-12v-528w-atx-12v-v2-31.html
http://www.rebeltech.co.za/index.php?main_page=product_info&cPath=30&products_id=1793
RAM: Just add another 4GB stick ~R400
Keyboard: ~R400
CPU: I played on a H61 (and H77) and i3-3220 for almost a year with my HD7870 Myst, had no problems in games, GPU took most grunt. However, upgrading to my i5-4670k did see some FPS increases in some games. I'd suggest upgrading your CPU and Mobo together in 6-12 months. Thereafter a SSD.