Bwah? How did you get light blue Marth? And why are you playing on Corneria against another Marth?
If you grab at low percents, fthrow to regrab to uthrow instead of grab to uthrow. Free damage.
You're fsmashing a lot... I mean... it's working out for you so far, but it's not a very good idea. When you're in the middle of the stage, the most you'll get from an fsmash is twenty damage. It's unlikely that you'll kill them at low to medium percentages and you probably won't be able to get there in time to edgeguard. Two fairs add up to more than that much damage. So combo instead of smashing.
Ouch dude... don't get fthrow chained... DI down and away.
JC your grabs.
Utilt is a good move, but try to aerial combo instead, as it's more sure and generally leads to better options, especially on floaties.
Your approaches are really high... full jumps and double jumps will telegraph approaches way too much. Dash dance a little, then go in with a shffl'd attack or a JC grab instead.
Also, don't dash attack as an approach.
You Counter a lot and it generally doesn't work out so great... try... I dunno, spotdodging instead.
What's with the song? They're talking about like... liberating bananas...