Maybe $500-$1000
Start with coinbase they a major exchange/crypto bank site than can go directly into your bank account.. Now you should be able to invest directly into crypto on coinbase alot of the others are not hosted on coinbase you might need to go to binance but beware binance has an issue with U.S. users even on the usbinance site. Gemeni.com is still available and kucoin... Also look into trustedwallet it is a storage site directly connected to your cellphone you can put your coins on..