How to make my pc play games better without hardware upgrade?

Okay so witcher 3Gentoo coming out next year, but I don't think my pc will be able to run it at high, so I want to try to make it play better with my 6870 1gb also witcher 2, is it possible for any driver swaps or system editing or even changing the distro to make my pc able to run it ? I was thinking gentoo with custom kernel? 

Also I would like to ask, how can I install borderlands 2 goty with PoL? Under gentoo? 

Thanks 

There isn't really a way to make your computer as good as buying a new one. Even overclocking doesn't make a massive difference without exotic conditions. But overclocking and a few other things can help you get the most out of the computer that you have. Right now I can think of the following possible performance improvers:

overclock your stuff

make sure you have a recent kernel, driver and xserver,

check top to make sure you don't have anything chewing up too much memory or too many CPU cycles

make sure your swappiness is well configured (if your computer swaps too early the game will load slowly because it will need to access data from the hard drive that really should be in ram)

 

Does anyone have any other ideas?

Does anyone have any other ideas?

Nope.  Overclocking and lowering occupied system resources is about it.  I don't think Witcher 3 is going to support Mantle, and even if it did, your card doesn't support it nor does Gentoo or any linux version at this point afaik.  There's also no guarantee you would see performance gains with it anyway.  You can try and make sure your hard drive has plenty of space and isn't fragmented, but that's really only going to help load times, and only minimally.  There's really no magic switch that can be flipped to make your computer perform better, other than overclocking.

What I would do if I were you is install a lightweight environment.  One like LXDE would work since it uses less resources.  It would make it so there is more power to be dedicated to the game than the system. But, I can't make any promises.  Good luck!