Purge's guide to support Skywrath Mage
Skywrath Mage is a quick but squishy hero who can play either mid or support. His support is pretty strong if he builds arcane boots because you can move around the map and kill enemies with a simple combo of Ancient Seal and Mystic Flare.
Try to pick Skywrath in combo with stun allies, roam around the map getting kills, and during fights try to kill 1 enemy right away at the start of the fight. Make sure to ward and buy sentries when you can, since you are supporting!