What PSU and GPU do I need for this PC?

I got this bought for me from my parents: http://www.ebay.co.uk/...1294273175, its a mini PC so unfortunetly they are horrible to customise. I want to play my steam games on it, like CS: GO and GTA V. I'm wanting a graphics card that will fit the mini case (preferably a 3GB or 4GB card, i'm aware it will bottleneck because my cpu is only 2.4ghz), and i'm presuming ill also need a new psu, which will also have to fit. I've already ugraded the ram, do you guys know any graphics cards or psus that will fit that are cheap as possible (i'm pretty broke)

Nothing you can do to it will make it gaming worthy besides just replacing everything in the case, including the case it self

Sadly this PC is not worth upgrading, it is a small form factor, any graphics card that will fit will barely be better than you currently have, similarly you are limited to a SFF PSU made by levono.
Don't waste any more money on this computer

That system uses a 65W brick on a rope power supply that can't be upgraded. It could be ordered with low profile versions of the GT 620 or R5 235, but those are likely low power, detuned, OEM variants that would be difficult to locate.
http://shop.lenovo.com/...ifications
http://www.newegg.com/...6883265827
Sorry, but that's the wrong system to try to upgrade.

That is a "small form factor" system (SFF). You can't upgrade the PSU, those are custom made to fit the case (standard PSU will not fit). Then, any regular GPU will not fit either, only low profile video cards will fit. Low profile cards are usually low end video, not worth the effort…