hey, I used to main lucario, and now I quarternary him. here's my advice:
dair can be used as a spike if they're right next to a ledge, similar to dk's cargo throw, they will bounce off. approaching is difficult, I recommend using baby aura spheres to make them approach. or try to get a long-ranged fsmash or bside. good stuff is fair combo, but you'll want to do a fair into nair if you shorthop, then you can follow up with a b-side grab or neutral a on the ground to keep them guessing. if a fair approach fails, you can drop back in the air and do an fsmash in case they try to come at you from the ground. his grab range is crap. all the smashes are slow. upsmash has crazy hitboxes, downsmash is eh, but is pretty strong and hits them at a good angle, but no range.
use uptilt, it is your friend. on heavier chars it can be like shiek's f-tilt. air movement is slow, and dodges are loong. don't try to dodge if you want to be able to hit them after, really only if you're trying to get away, because they will probably be ready to attack again by time you get a fair out after an airdodge. Back air has good range, ftilt is a good mix-up attack, takes awhile to come out, but can be surprising. bair is good for doing right as you land. DI is more important than w/ other chars because you'll want to survive longer to use your aura damage-power ability. ledgeguarding is good against people with slow-moving b-ups or recovery moves because you can sh off and fair 3-4 times till they're too far to get back, then you can use your second jump which is pretty high then b-up to get back w/ relative ease.