Always feel free to contribute! Even if you don't have a ton of experience, your opinion opens up discussion and gets you involved. Besides, you probably know more than you think you do.
My random thoughts on the MU:
Even though his jab is fast, our ground game still beats Luigi's, imo. Most of his jab combos can be avoided by proper SDI, which is really important if you don't want to get jab > Shoryuken'd. Dtilt, fsmash, and grabs work well while you're on the ground.
As for spotdodging.... well, spotdodging predictably at close range is something you shouldn't do vs. any character, so that was probably a case of you abusing it to the point where he could easily read you. Still a good warning for others, though!
In the air is where Luigi gives us the most trouble..... his aerials beat ours, and his laggy *** boot (nair) is a legitimate combo breaker when used with good DI on his part -- it comes out on frame 3. I try to stay grounded as much as possible in this matchup, or if I'm in the air, I stay underneath him to land uairs.
His tornado goes straight through tjolts, so be wary of camping at mid-range, especially since the last hit will pop you into the air (which is bad) if you don't DI out of it. If he tornadoes while you're grounded, just shield it and punish its horrible end lag.
Be.... really, really careful when recovering vs. Luigi. Skull Bash is generally a bad idea, because if I'm not mistaken, his bair will always beat it. Maybe his nair too, but I'm less sure about that one. QA also has horrible priority (as always), so combined with how laggy his nair hitbox is, your best bet is to just QA around him.
I dunno much about edgeguarding Luigi (my edgeguard game is pretty garbage atm.... still working on it), but if he has to tornado for vertical height when he's forced to recover low, he'll usually end up lagging above the ledge. Punish that.
He has more killing power, but his KO moves seem to be ~equally as hard to land as ours if both sides know what to watch out for. Fsmash and up b hurt the most, but barring bad DI out of his jab combos, he'll have to rely on predicting a roll/spotdodge/bad tech choice to land either one of them. His aerials are strong too, but none of them jump to mind as being overpowered enough to kill especially early.
Our camp beats his. The only thing you have to watch out for, like I said, is his tornado, but if it comes to a camp war..... we'll win.
For stage CPs, I like Frigate and PS1. Dunno what I'd ban.... probably Brinstar just because I hate the stage so much. *shrug*