Risky
Smash Ace
Yes DA leads to anything, it's the first attack in his mechanic. As Lucario you should be able to convert off of almost any hit you get, it's how he's designed. Whether that conversion is just a tech chase after a knockdown or a legit OHC combo doesn't matter that much. Yes it's a good approach, probably his best one, but he has a lot of other options you should try to explore instead of centering your playstyle around that move. It would be similar to saying Fox should always be trying to Shine as an approach because it's his most versatile linker/combo starter.
"Yeah dash attack is pretty key in the approach, fair doesn't really give you anything at low percentages so not many other choices."
Aura Sphere, Throw, Fair, Dtilt, to a lesser extent Utilt, spaced Bair. These are options without charge. Not sure why you say that about his Fair, as it leads to FP, a 2nd aerial after you ASC, a throw after you ASC and FF, DT mixup, even Extreme Speed if you want. All of these naturally depend on spacing and matchup.
"Yeah dash attack is pretty key in the approach, fair doesn't really give you anything at low percentages so not many other choices."
Aura Sphere, Throw, Fair, Dtilt, to a lesser extent Utilt, spaced Bair. These are options without charge. Not sure why you say that about his Fair, as it leads to FP, a 2nd aerial after you ASC, a throw after you ASC and FF, DT mixup, even Extreme Speed if you want. All of these naturally depend on spacing and matchup.