I main Mario and use him a lot on For Glory. I´m great at doing air combos, edge guarding, and value the cape and Fludd shenanigans. But I can´t manage to land his side air, every time I try to spike they either air doge or just jump over it. Since its slower, I figure that its easier to avoid than others. Does anyone have any advice on landing the meteor smash successfully and when to do it ?
Mario's Fair is pretty easy to see coming, so it's easier to land it when the opponent is recovering, when you read an air dodge, or when you use a setup. Some characters (e.g. Captain Falcon, Duck Hunt) are pretty vulnerable during their recoveries when they're trying to get back onstage, so you can Fair them if you time it right. I don't really have any tips for the timing; I think it just comes with practice. Note that you can also stage spike characters by Bair-ing them into the slanted bottom of a stage. They'll bounce off the slope and, if the opponent doesn't tech it, it can almost be as effective as a normal spike. It's way easier than Fair in some situations, so it's worth a mention.
Air dodge reads are a bit situational; people can generally tell when Mario's going for the spike and jump instead. You might be able to do it during an Up air string, for example. If the opponent generally uses air dodge to escape your combos, you can usually expect them to do it the next time you do a combo. While you're doing Uairs, you can pause and wait for the opponent to air dodge, and that's when you Fair them. Most of the time it won't be offstage, but it can work for extending combos or for just looking cool, I guess. Oh yeah, if the opponent air dodges your Fairs, then delay the Fair so that you can hit them. Won't work all of the time, but it might work every now and then.
I don't really know about Mario's setups into Fair. I've heard about Dthrow > Fair at some percents and rising Uair > Fair might work, but I'm not so sure about it.
Most of the time I just get spikes while edgeguarding: if you got the timing down and if the opponent is mostly vulnerable, then you should be able to dunk them.