In terms of good mouse a low price would be around 30€.
As for the ones you list the a4tech were regarded time back as decent mice but with very cheap materials (in many cases not lasting long, that is).
I see in #25 that you are willing to go up to 25€, add a little more, taking into account the mice listed in #14, and I don't think you will regret it.
Those mice are fairly cheap and for that price it would be hard to get something decent. Aim for something that you think will fit your hand comfortably. Other mice will surely cost a little more. How much are you considering spending?
Hmm I don't know if you can find something at that price in Portugal ( I live there too ), all mice at that price are Microsoft ones which are very small and not good for FPS games.
This is definitly better then the Oscar at least the shape. But I don't know man, if you want such a low price mouse then it is up to you to choose what you want .