If you live in the USA Gemini and Coinbase are your only decent options for buying crypto with USD. I recommend Gemini because the fees are lower. Deposit money with your bank account to minimize fees.
In crypto security is your own responsibility. You absolutely must use 2FA on any exchange you have money on. Write down the code with pen and paper. Read from the paper and put the code in your phone's Google Authenticator. Keep the paper backup in a secure place.
Use a VPN for added security and to hide your location. Opera has a free VPN that works well.