If you want to upgrade the whole PC, and you want to use it for games, you may need $300 to $400 because you need the new GPU + PSU + OS ( if you use the old MB you don't need the OS). You can use the i5 3350p, HDD, DVD drive, RAM, maybe the MB, if you need the new case or better GPU than the budget will go up too. Like the lower budget upgrading like R7 265 or gtx750ti, a good brand PSU, win7 or win8. Because I don't know where you are, I just post them in USA $.
[PCPartPicker part list](http://pcpartpicker.com/p/C492zy) / [Price breakdown by merchant](http://pcpartpicker.com/p/C492zy/by_merchant/)
Type|Item|Price
:----|:----|:----
**Motherboard** | [Asus P8B75-M/CSM Micro ATX LGA1155 Motherboard](http://pcpartpicker.com/part/asus-motherboard-p8b75mcsm) | $67.99 @ Amazon
**Video Card** | [XFX Radeon R7 265 2GB Video Card](http://pcpartpicker.com/part/xfx-video-card-r7265acnj4) | $109.99 @ Newegg
**Power Supply** | [Antec Neo Eco 620W 80+ Bronze Certified ATX Power Supply](http://pcpartpicker.com/part/antec-power-supply-neoeco620c) | $39.99 @ Newegg
**Operating System** | [Microsoft Windows 8.1 (OEM) (64-bit)](http://pcpartpicker.com/part/microsoft-os-wn700615) | $89.98 @ OutletPC
| | **Total**
| Prices include shipping, taxes, and discounts when available | $307.95
| Generated by PCPartPicker 2014-10-12 13:58 EDT-0400 |