Gaming PC

Yep if you really wanna enjoy some good MX games going for a pc that can run games optimally sure is a good choice. Mx Simulator is king for me, all the skins, races , replica tracks, events etc ... It's hard to learn to ride good in the game but very rewarding once you learn to do so.
Other Mx Games choices you have is Mx vs Atv Reflex, they have a quite good MOD community that make tracks and stuff for the game, there is some good youtubers around that show some nice stuff in that one. And ofcourse the new Mx vs Atv supercross will also be on PC so thats another one to play. There is also that one game called Mx-Bikes by Piboso but i never really got into it, could be fun to check out though.

As for specs for a ''cheap'' game pc. You should atleast wanna spent around 600-800 Euro to be honest to get some value out of it. There is many websites that have prebuilt stuff to get an feeling for what you can get for that kind of money. Some things to look out for (i am a Intell & Nvidia fan) are this: Atleast an i5 CPU mid end range. An GPU of the 'x60' series, like the current nvidia gtx 960. 8-16 gb ram at 1600 mhz. Thats pretty much the core components you want to aim for.

Ofcourse you can go for an SSD hard drive for crazy startup speeds etc, but if you are on low budget shouldn't be a priority.

If you really wanna save money the counterparts to Nvidia & Intell is stuff from AMD, i am not really a fan of them but they are sure also reliable and allot cheaper so it could be a good alternative. You can save a couple of hundred bucks by choosing this brand. (the R9 series of AMD are really good graphic cards).

Best thing you can do at the moment i think is look around the internet for pre-builds and look at the components they have in it, do allot of comparing and see how much you wanna spent.

To compare my pc is self built and was around 1400 Euro, with the following stuff in it: (can run mx sim in full hd 40 man gate online)

Intell I7 4770k with Corsair H60 water cooling circuit (i dislike the stock intell cpu fanns)
16gb of Corsair RAM memory at 1600 mhz
Nvidia Gtx 770 (will upgrade to a 900 series card at some point, probly a 970 or 980 depending on money)
SSD Samsung Evo 512 GB
SATA HDD Western Digital 2TB
750W Power Supply
Some Gigabyte mobo of around 150 EU that supported my CPU socket
2x 1080p 60hrz 24'" Monitors of LG (double screen is really sweet on a gaming pc, browser for VitalMX and other screen for games / Streams during races etc ... )
etc ...

Anyway you'll have to do allot of research and set a goal of how much you wanna spent, there is lots of sites where you can choose all your components yourself and see which price you get!