Wifi is usually terrible. Practice tricks offline. That's the only way to get better.
I can't really tell you how to use FLUDD properly...it's a situational move most of the time....you can gimp bad or predictable recoveries with it, and you can mess up spacing and projectiles with it.
Actually there is one trick with FLUDD that very few people apply, but it can really save you when you are recovering. A lot of people like waiting for Mario to air dodge after he ledge jumps, and this is probably because after sweetspotting the ledge with Up-B, Mario still retains a landing lag animation the next time he touches the ground (which you can bypass by landing with aerial attacks instead). Another way to work around this lag is by ledgehopping with the FLUDD charge stance, and this allows you to shield or roll without the landing lag.
I wouldn't count on Jab locking, but N-air can set it up occasionally.
Fullhop D-air is in general quite useful. It has no ending lag so it cancels into anything you want. This is very good for baiting air dodges.
SH D-air can cancel into a N-air or U-air if you buffer it correctly. Mario can also do 2 B-airs/U-airs in a short hop, or one B-air/U-air and a N-air before landing.
