I had a match recently with a Mario player. I lost the match, but I did have a good amount of momentum for the duration of the match. The problem with Mario is that he is good at dealing with floaty characters. The main thing you want to watch out for is his fair spike. My strategy was to limit edge combat on the stage. At the beginning of the match, I felt it was my responsibility to control the center stage by any means necessary. Use your best judge of character depending on the situation. If Mario rolls a lot, I think it would be best to have a turnip in hand so you can punish him even if he shields it. I think I did too many short float dairs. That's what cost me the match. But I'm still a strong believer in this strategy.
Also, I recommend using turnips as your primary edge guarding tactics. Only go off the stage if you're 100% certain you can get the kill. Watch out for his fair.
When you recover, you definitely don't want to be out of Mario's range for his fair spike. Either recover super low or super high. I say this because Mario doesn't jump very high and he can't afford to go too deep.
I hope this helps. I think controlling center stage is a good strategy for all characters with spike moves. Perhaps consider this for really good Yoshi, Donkey Kong, or Captain Falcon players.