haha i secondary luigi so here's some advice
- never take to the air, holy f*ck luigi is too **** good there. if you're in the air, shoot a laser or plan to do a killing move; the latter you HAVE to make sure it hits otherwise you're in for at least 2 aerials
- careful about distancing yourself, luigi tornado is ridiculous in terms of priority (i'm pretty sure it clanks with whorenado) and travels a lot quicker than you expect
- don't get too shield-drop happy at higher percents, luigi can do a number of setups -> upB or can upwards tilted fsmash you
- for the love of god do NOT pick BF or YI against Luigi. platforms belong to him; a good Luigi will abuse the UpB through the platforms when you're least expecting it. not to mention his recovery is phenomenal due to the lack of janky edges there, he'll slide up on them with the tornado while making approaches impossible. also yoshi's island is just a really good stage for Luigi in general; I think its just the fact that his tight control over the small stage helps a lot
- what you should pick, instead, is something like FD and SV where aerial control is a lot more limited and where your lasers can control the approach. if you really want to f*ck luigi over then go to lylat, it's impossible for him to move on there without getting attacked by Falco - the tilting and the weird platforms make you faster than he is
- make sure to use ftilts and shines to space, it's also a smart idea to use utilt once in a while to toss him up above for a bair to bait the airdodge; it'll either go through or you can dj -> instabair for a nice sweetspotted 13%
- do not underestimate Luigi's recovery. It is phenomenal in terms of distance gained and for Falco it's difficult to get inside it