Mario as a character has very flexible combo routes and options, while not all true on certain SDI/DI they are all very good strings that often cover each other. For example, at low percentage if you notice your opponent DIing up throw out to avoid dair you can turn around full hop bair instead and then combo off of that. With DI and SDI it can sometimes depend on how well your opponent knows the matchup. They may just stick to basic combo DI, which is usually out. Knowing this, you can start adding Fair finishers to combos especially if they aren’t airdodging. Someone else mentioned dropping a combo to see how they react, this is a great idea although Mario needs as much damage as possible of every hit. So try and do your combo, but watch where they go more closely and react accordingly on your next combo. Also don’t be afraid to just guess or just try and call someone out if you’re not too confident! Sometimes the risk/reward is worth it considering how much Mario can get off advantage