Masterplum
Smash Apprentice
heres a good use of neutral air. hit with only the first part as youre landing. so jump, fastfall, then neutral air so you only use the first hit. Pretty much like what people do with falcons neutral air but marth has more options afterward since most of his attacks come out faster. This can lead into d-tilt, jab, grab, d-smash or others but those 4 are the best followups. go try it youll prolly find yourself using it to approach often instead of the common f-airs used all the time.