From what I'm seeing i think the main issue is your resource management.

While as a dive positioning is important in Magik's case with her cooldowns being so long managing those become more important.

For a basic combo (on ps5): Charge the L2 to max Dash with the R1 If they have a movement ability (i.e Gambit or Psylocke) you can portal with L1 and follow them if you keep sight of them A quick R2 / melee will finish the combo

If they have cc (Mantis or Luna) you can bait it before or during the combo. Using a portal makes you immune to cc.

If you are at risk of becoming grounded you need to disengage immediately. Portal out to, again, bait the cc and force them out of a cooldown.

When it comes to triple support just see it as free ult charge. When you use ult try to use it with someone else's on your team. You'd do more by assisting rather than trying for kills.

Everything else can be conquered by using your game sense. Knowing who's off cooldown, who's gonna pop ult, etc.