>>25055224SMTIV is very newbie friendly while still being decently challenging
fuck Beelzebub so it's always a good place to start. The Persona games are good as well, especially 3 or 4 though you'd want to make sure you get the "director's cut" versions with Persona 3 FES and Persona 4 Golden.
The Devil Survivor games are great but they're SRPGs like Fire Emblem or Xcom compared to the standard turn-based ones. They also have a tendency to be pretty brutal if you've never played an SMT game before so just keep that in mind, but they're probably my favorite spinoff games.
SMT1 also got an iOS port if you want to check out the earliest entry with an official English translation and have an Apple device, but obviously with being one of the earliest games in the series there's some mechanics that are weird by today's standards.