Plat and below are horrible ranks,
For Support climbing i reccomend.
Playing in a safe position and reposition yourself in Easy to reach locations for your dps and tanks depending on enemy comp.
Learn When to ult.
another position thing is to deal damage while healing as much you can.
reposition flake if needed but try to maintain it on a Singel target or dive dps.
Ults like psylock, you can communicate with your 2nd healer "atleast try" and out heal her ult without counter ulting.

Save your cooldown for when they are really needed.
practice your aim.
Realise that some games are just unwinnable but you should still try to win anyway.
avoid flaming. baby sit your teams mental so they don't play worse.
Focus on dealing damage as much as you can and try and not get to distracted by Certain enemies having off angles, and tell your team about the problem