Yes the Pain of CSGO with Ping - i had that a lot in past - but i have 250kb connection(
i Know i am the lagger in every match FORGIVE ME PEOPLE I WISH I CAN CHANGE IT ) - the ping sometimes reached 700 suddenly !!
that happened to me one time after i was having 160 ping - and suddenly it became 500 - 700 after new update from the game
so i thought the problem from the game - checked the files from steam ... nothing changed it even became slower
so i found that my windows Pc ( windows 8.1 that time ) was automatic updating - downloading all stuff in background - very large one i believe that was for updating to windows 10 -- so it was killing my connection
so stopped widows update - didn't help anything - so i let the device finish download - also my Antivirus was updating a lot taking more bandwidth
after both finished download the Ping returned to 250 - didn't get back to 150 until device updated to windows 10 - just for few days and the pain started again
so if you can some how check what actually using internet in background and stop it - your problem solved
also general steps like closing torrents - downloads - disconnect other devices on network .... etc