If Emblems return please make them relevant to the characters of that game. The FEH approach to Engage limited the develoomemt of that game's new cast.
I've visited gamefaqs and while most people agree the story is very basic some like say not caring about character backstories or a good plot just wanting to do gameplay.
A direct is tomorrow hmm that FE 4 rumor might be real... As for your question I usually don't waste money on stuff until I get enough to save so I would hold off on buying stones imo.