How does cancelling a credit card impact my credit score?

Yea actually, i am thinking of cancelling my first credit card. Devalued too much to be lucrative

Cancelling your oldest credit card will reduce your credit age. Which will slightly reduce your credit score. Unless, there is another line of credit which isn't too new, >2y from oldest line of credit, then your score will only drop temporarily. If it doesn't cost you anything to keep it active, maybe you shouldn't close it.