You wrote a six word question, with no details.

The answerss can range from "take your 20 bucks to a Bitcoin ATM", to "to do that large of volume, you would work with a broker who will put you in contact with the seller."

In between those two are 100+ variations, depending on what amount, what frequency ... like is this one time or recurring purchase, what payment methods you have, how important is financial privacy to you, (and what degree of paranoid is justified), how soon do you need the coins, etc.

So the tldr is probably ... azteco if that exists in your area, or Find a Bitcoin ATM that you can pay with cash no kyc, and if you don't like having to give them your phone number there are other privacy tools for that too.