Help needed buying an oscilloscope

Hi guys,

I am not from IITB but i thought this is the best place for this question.

I want to buy a good oscilloscope and see a lot of youtubers have a pricey scope compared to those available on Amazon. I am from a CS background so I have a long way to go but I worked with scopes in my 1st year of engineering.

What I want to know is looking at the sampling rate and the frequency on the scope. The scopes i checked out has 1GSa/s sampling rate. Can you tell me instances when that would be insufficient?

Also the same question for the frequency.

Thanks