Most of the focus has been put on picking up Fire Emblem Awakening and Fates but I just want to remind people not to sleep on Fire Emblem Echoes: Shadows of Valentia
Picked this up in 2018 and I highly recommend it if have even a mild interest in the series. Because it's a remake of the 2nd game, it's unlikely to well...get another remake. So this may be your last chance to play through the story of the 2nd game of the series. As it was typical back on the NES, this game has many differences compared to the formula established in the first game, like the weapon triangle being removed for example. But it also introduced a lot of elements that would sporadically appear in future Fire Emblem games like an explorable map. There's also segments with full free roaming dungeon exploration. You'll explore with a behind back camera but when you enter battle, if will be your standard Fire Emblem tactical battles.
It's faithful to the original game, at times, to a fault. The maps aren't the best in the series and you may find a lack in depth compared to other entries. But despite that, it's still the tried and true Fire Emblem formula at its core. Plus this game introduced some modern quality of life options like rewinding turns. You can customize the difficulty to your liking.
But I think the main reason to play through this game is the story and presentation. While nothing groundbreaking, it's a fun and epic journey with the game's dual protagonist Alm and Celica, who are among the top fan favorites for the series. The presentation was also a step above Awakening and Fates in that nearly all of the dialogue is spoken, even in minor scenes. And in my personal opinion, it's my favorite soundtrack of the 3DS game and even beats out the Switch games.
The game isn't without its warts and Awakening is still the better pickup if you can only get one 3DS Fire Emblem game. But if you have the spare cash and time, I think Echoes is worth taking a look at.