frozen cradle
Three houes is amazing, some people will find it too easy but overall imo it's one of the best FE if not the best especially for the story and overall themes. The level up can be fairly quick, especially in normal mode you can do infinitely some skirmish battles so you could just grind those.
The DLC is a separate story with different characters so it doesn't help you in the main game (tho if you finish the DLC and start another playthrough afterwards you can recruit those new characters in the main game)
sick shard