diving a little deeper into the specifics of recovery. I have some trouble getting shine spiked a lot. I am by no means anywhere near where I need to be with my recovery mix ups, but it seems like i get gimped by shines way too much. any advice or tips on avoiding these?
Yes. Despite shine spikes being super deadly Marth has great tools to counter it. The way you actually counter it is highly dependent on situation.
First we start with being shined off stage. Simply FF when you reach the ledge and you'll snap to it, no problem. It gets possessively more difficult the close to the edge you were shined but nothing a little practice wont fix.
Next you have to keep in mind where your coming in from. High or low, Double jump or not, far or close to the stage. All these things play into a good recovery. Lets eliminate being far from the stage because fox doesn't wanna jump all the way out for the spike just yet. We can also safely say that he wont jump high to shine you because you can still just fall back, DJ and recover low.
Now we know that to be spiked will likely be low at a close proximity to the stage. If You are a good Marth and kept your DJ you can simply swat fox away. This is awesome because if you get the week hit of DJ fair then fox falls below you and you can get your own gimp with up B. If you don't have your DJ you might have to do an early up B or catch him with a side B.
(remember to side b close to the stage very VERY conservatively... it'll get you spiked.) Of course Fox can be very tricky. He can CC an up B and just shine you away to death. In this case sweet spot is an option, but that is risky as well. Fox can also shine you from behind your up B tho it's dangerous, but if they are consistent you will die many many times. They can also refresh invisibility to avoid being swatted from the ledge and spike you there. lots of mix ups.
Long and short Raising aerials and Up B mix ups to intercept the shine spike is the standard strat. Don't side B too close to the fox. If you get CC shined out of up B... it happens i guess.