Looking for a headset for csgo

I strongly recommend Audio-Technica ATH-AD700x for online/competitive FPS gaming; it has a very big soundstage and great imaging, separation, clarity and detail retrieval. It has a bright sound signature with recessed bass. It's open-back, over-ear, very lightweight and has a durable construction and replaceable earpads. Attach an Antlion ModMic 4 and you have headset. The mic uses a clasp system to attach to headphones and is easy to attach and remove. It's compatible with all headphones and has a mute switch.

If you can't afford this headphone, then I recommend Superlux HD668B with velour earpads from HiFiMAN. Also look into AD500x.
I do not recommend HyperX Cloud / Cloud II / CloudX because they have a terrible price-performance ratio compared to AD700x and a very bad one compared to HD668B. The Clouds have a small soundstage, bad imaging, and they sound very muddy with grainy bass.
I also compare to AKG K52, AKG Q701, Beyerdynamic DT990 (600 ohms), Philips Fidelio X2, Philips SHP9500, Sennheiser HD700 and Superlux HD681 EVO. I got all of these headphones for gaming. I can't emphasize enough that perceived performance in headphones/headsets is relative.

Closed-back headphones have cups with solid shells that largely isolate sound from passing in and out.

Open-back / semi-open-back headphones have cups with perforations/grills that allow outside sound to freely pass in and sound from the drivers to freely pass out. How loud you hear outside sound and how loud people around you hear the sound emanating from the headphones depend on your volume, of course. The sonic benefit to open-back is generally a big soundstage.

Soundstage is perceived space and environment of sound. It can be compared to virtual surround sound; both attempt to produce the same spacious, three-dimensional effect. VSS can sound more ambient and immersive, which depends on the processor (CMSS-3D, Dolby, SBX, etc.), but it degrades the sound quality and diminishes detailing due to compression from digital processing. You might also experience less accurate imaging and separation if the headphone already has good imaging and separation. Note that a deep soundstage is equally important as a wide soundstage.

Imaging determines how accurately sounds/objects are positioned across the soundstage. And I mean where they are positioned and not merely what direction they come from. This distinction is important because only being able to tell what direction objects come from is to me not good enough when playing against people or on high difficulties.
Imaging is inherent to the audio content, so if the game is recorded or mixed poorly, a headphone with good imaging won’t improve the positional audio, so don't judge the headphone before using it in several games you're very familiar with. I test mine mostly in Battlefield: Bad Company 2, a game that has great recording and mixing and that I've played for over six years.

Separation is separating individual sounds from a range of sounds. Good separation makes it easier to filter out or discern overlapping sounds from other sounds and track them.

Sound signature is a frequency response / sound profile. For example, a V-shaped sound signature emphasizes the bass and treble while recessing the mid-range. A flat/balanced sound signature doesn't over- or under-emphasize these frequencies and attempts to reproduce the original recording accurately as possible. A bright headphone emphasizes the treble and can subdue the bass. A warm sound signature emphasizes the bass or subdues the treble.