On Luigi...
DownB apporach is a *****, counter with Toad if you see it. Usually, Luigi players seem to like apporach mid away, right outside the turnip throw range and do it since it's used as an apporach, a punisher, and a damage racker. Either that, or timed Dtilt or Ftilt. Fsmash is too slow to punish the DownB apporach.
Fireballs go straight and only straight, so when grounded, float over it. When Aerialed, Dash attack. Watch out for the sudden Usmash that Luigi has. It has great priority.
Fsmash incoming! Play defensively at mid-high percents because Luigi's knock is expotential at mid to high percents, espeically Fsmash, Usmash, Fair, and Sweetspot UpB.. Both the jab -> Sweetspot UpB is hard to avoid if you get caught, and Luigi spot dodge to Dsmash/Usmash is very powerful. Don't worry too much about Dash attack since he can't combo it into a Sweetspot UpB anymore if he hits with the final attack since it has be upgraded to have knockback.
Luigi's Dair spikes! Ahhh!!!!!
Never underestimate Green missile (sideB), it's very high in pirority.
Never underestimate Luigi's Recovery. His DownB can recover so well, it's like IC's Side B except it covers more vertically than horizontally.
45:55 favor Luigi, but then again, I suck against Luigi, so it might be just me.