This is not a easy answer

As ON-ramping with FIAT is country specific now

nobody will document all local solutions here for privacy reasons.

https://bitcoin-intro.com/ - looks fair

Key is to use basic mainnet wallet only as first time self-custody user - Bluewallet on android + IOS best to start. GetAbly LN-Wallet and Sideswap LQ-Wallet. Green-Wallet with JADE next to learn