Many exchanges with kyc offer to buy low amounts of bitcoin. 
You can also set a dca,  choose the amount and the time of purchase, 1 time every week or 1 time every 15 days...so you don't even have to think of purchasing bitcoin and don't care about the price.

depends of your location try: in the u.s. many use cashapp or river, strike.
In europe & rest of the world: relai, mtpelerin, binance, kraken, bitget.

You can also check peach bitcoin app and robosats, they are more anonymous because it's peer-to-peer, no-kyc, the app connect you with someone who want to buy or sell bitcoin. I'm often on peach, you can use my referral: MOON21 to have free first transactions
https://peachbitcoin.com/fr/referral?code=MOON21