Gaming mouse are usually around 50-60euro.
I have Zowie Fk 2, coming from Zowie Fk 1 and I wouldn't want another mouse brand, simply love them (but that's preference) I use fingertip grip. If I had palmgrip, I probably would've went for Logitech, as I like that brand more than razer.
Top tier gaming mice brands are: Zowie, Logitech and Razer.
What kind of grip are you using as that kind of helps in recommending a good mouse.
Mice you could be looking at:
These are one of the best currently, they have the latest optical sensors and a good feeling/build.
(avoid lasor sensor by all means, steelseries uses it in almost all of theirs).
Razer deathadder (Palm-grip)
Zowie FK 1 (Palmgrip)
Zowie FK 2 (Fingertip and Clawgrip) [This one is a little smaller than the FK 1]
Logitech G400/G400s or newer G versions (Palm Grip)
I can probably recommend more and Zowie also has other series than the FK (which I believe for bigger hands), but i'd take a look at Zowie if you have fingertip or clawgrip and Logitech G series if you have palm grip.
What to look for in gaming mice:
It kind of depends on what kind of grip you use and how big your hands are, there is nothing worse than having a too small or too big mouse. Also you have to be looking at the sensor, Optical sensor -> Laser sensor. Laser sensor have built in (hardware) acceleration that you can't turn off by software, which you really don't want, in none of your games. Avago is the most used optical sensor brand and you should be looking at Avago sensors. The mouse I recommended above also include them.
If you go for a crappy mouse, you'll probably lack build quality or a good sensor. so i'd personally go for 20euro more and go for one that'll last you some years. Ofcourse even a 1dollar mouse will be able to work as a mouse, but it won't be as accurate which is required for high level of play, especially in games like Osu, CS:GO where aim is extremely important.
Grips:
http://blog.ncix.com/wp-content/uploads/2015/02/IRu7OnD.png