There is a lot of different mice you can buy today with only 10 €/$ and they will work pretty well but investing 30 €/$ for a cheap gaming mouse does not sound bad either.
Mice are pretty cheap compared to other gear/components but that doesn't mean they aren't important.
Having a better mouse will usually give you advantage in games and are more comfortable than cheaper mice.
I cannot say what mouse is the best and what you should get but I recommend to have a mouse that have specifications clearly listed on internet/guide so you know what kind of device you are dealing with.
In gaming mice you can also customize what specs it will use with a driver software.
You should at least know the DPI/CPI the mouse uses.
Also refresh rate (polling rate Hz) is somewhat important if you are looking for best performance.
Other stuff doesn't matter that much for the actual performance but it is nice to have features that you might want.
Mouse pad/mat is very important for your mouse performance and they cost about 20 €/$.
It doesn't matter which mouse you have good mouse pad can improve your mouse accuracy even more than buying a new mouse.
And I really know that because I used to play on a smooth table I thought was good and it really was pretty good after all but mouse pad took it to a higher level.
I recommend to have gaming mouse pad because they are much better quality and value than classic rubbish mouse pads.
Usually gaming mouse pads are also larger than usual and I highly recommend buying as large pad as you can fit in your desktop.
Wider than 355 mm or about 14 inch will work perfectly but if you are cool with lifting mouse or using higher sensitivity smaller pad will work just fine.
DPI (dots per inch) also know as CPI (counts per inch) tells how accurately cursor/crosshair reacts to your mouse movement.
High dpi means that if you move your mouse just a tiny bit it will react to the mouse movement.
When using low dpi you will need to move the mouse a lot longer distance to move the cursor.
There is no best or right dpi so the best way to test what is best for you is to try out different dpi-sensitivity combos.
For example if your dpi is now 400 and sensitivity 3, 400x3=1200, your combos value is 1200.
Now you must divide the value with your new dpi like 800 and you get same sensitivity but with higher dpi, 1200/800=1.
This way you can try out different dpis without losing your sensitivity.
And i highly recommend trying different dpis.
For example lowing down dpi might help if your hand shakes too much while playing.
On the other hand putting your dpi up might help to prevent pixel skipping because you can put your sensitivity lower.
The most important thing is to use native dpis because those dpis are will register the mouse movement without any software calculations.
Native dpis are mostly said in mouse's specifications.
At least the lower dpis like 400-1000 are native dpis for most modern mice.
Mouse Acceleration One of the most discussed thing is mouse acceleration.
There are 2 kinds of acceleration, speed acceleration and distance/time acceleration.
The first one and the more common one is the speed acceleration where the speed of your mouse affects the cursor.
This kind of acceleration is easy to test in-game.
Turn your guy fixed amount of degrees like 180 very very slowly and after that do the same again turn the guy 180 but as fast as you can see if the guy turns more/less degrees than before.
The second type can be tested by moving your mouse at the same speed the whole time and see if your guy starts to turn faster after the start.
It is very important to know if there is any kind of acceleration because there might be even if you have turned everything off.
For example Windows have option "Enhance pointer precision" in mouse settings that will cause mouse acceleration so keep that off or put raw input on in-game settings.
Putting raw input on only affects the game.
I personally recommend not to use acceleration just because then there would be multiple things that affect your sensitivity rather than just the distance you move the mouse.
Sensitivity Right sensitivity might be hard to find but there are 2 things that you need to pay attention.
First thing is not to have too high sensitivity.
Common mistake especially for beginners is to have so high sensitivity that your crosshair skips pixels.
Too high sensitivity can be easily spotted when trying to aim on a small thing and the crosshair skips it.
That's when your alarm clocks should ring and lower down your sensitivity immediately.
On the other hand if you find yourself lifting your mouse or cannot make fast turns in time that's the time you should use higher sensitivity.
Rather than trying to tell you right sensitivity I give you 3 example presets you might want to try out:
Low sensitivity, 90 degree turn can be made without lifting.
(480/x, where x is your dpi)
DPI/CPI Sensitivity 400 1.
2 800 0.
6 1200 0.
4 1600 0.
Medium sensitivity, 180 degree turn can be made without lifting.
(960/x, where x is your dpi)
DPI/CPI Sensitivity 400 2.
4 800 1.
2 1200 0.
8 1600 0.
Very high sensitivity, 360 degree turn can be made without lifting.
(1920/x, where x is your dpi)
DPI/CPI Sensitivity 400 4.
8 800 2.
4 1200 1.
6 1600 1.
Useful Console Commands sensitivity 1 - you can adjust sensitivity via console
m_rawinput 0/1 - disable/enable Windows speed and acceleration to affect in game sensitivity
zoom_sensitivity_ratio 1 - by default slows down sensitivity 1st scope to half, 2st scope to quarter
m_ - other not that useful mouse commands for tweaking