I can't seem to beat Matthias, i got really really close once but then i let my combos slip for a second she killed of me(Ruca) and ange, and only Iria was left at half health. Any strategies, also i'm at level 59, do i require more grinding -_-

You don't need any more grinding, but the battle as a whole will take a hell of a long time.

Instead of spamming Life Bottles, only use them in dire situations, or else just on Ange, who can resurrect others on her own. I always use Ange, so I can seamlessly resurrect and fight, but you'll have to switch and run away.

When comboing, It's more effective if you don't bother using Hi Ougi altogether. They're a waste of TP and Infinity Jams do more damage. Also, keep your Tension at max until a combo ends or Matthias becomes enraged, and then use IJ. This will maximize damage until it's impossible to string anything else together, and IJ interrupts pretty much anything. And when you do manage to get a combo, try to get everyone in there. Getting a 200+ combo is cake if you have everyone attacking at different intervals. Of course once you finish IJ get the hell out of there or you're screwed. I use Ruca/Spada as bait, keep the others away and guard until she calms down for another beatdown, but I'm not sure if you could do that in your case.

Free Run keeps your Tension maxed out. If you get into a situation where you can't do anything but run, and IJ won't do much, Free Run around the stage and it'll keep your Tension up.

Become as resistant to Earth damage as possible. The earthquake attack is probably the most enraging thing she ever does.

I can't really go back on shop for Earth capes, so i'll do what i can, and yeah that earthquake attack followed by the spinny sword really hits hard I always though Hi-Ougis did more damage, I'm not very good at getting everybody into an IJ combo, it always runs out too fast for me to do anything but a simple combo(Base>Master>Arcane) with two characters

Thanks for the advice though and i know the battle is so long -_-

Actually, using Master and Arcanes for an entire IJ combo is a waste of TP. Just use a basic combo+Base and switch immediately.
Watch video. Be enlightened.

I actually won just now, but thanks anyways I didn't even use IJ i just combo'd until i just couldn't combo anymore, and then when the gauge almost emptied i used an MA I played as Spada and used Ruca and Ange since i play best as Spada apparently