The usual build
These items are the optimal items for gloo with rapid boots used so he can chase the enemy and disengage right after, Cursed helmet is used so gloo can reduce the hybrid defense if the enemy he is using his ult on, Glowing wand is used so he can deal continuous damage on the enemy whilst reducing their heal, guardian helmet is used so he won't be too squishy so he can tank still tank some damage, Oracle is used so gloo can get more regen from his ult and combo, and Immortal is used so he can still survive after dying once
The usual emblem
This emblem setup is good for gloo because with basic common emblem gloo can regen his mana so he won't run out of mana quickly. Agility and wilderness blessing could help gloo to quickly disengage after killing an enemy so he can survive
Battle Spell
Gloo excels using flameshot because he can push enemies back when using his ult with flameshot so he can bring the enemy further away from their teammates
Best With Granger
80% co-op win rate
Granger is a good teammate for gloo because he can burst the enemy from afar while gloo uses his ult on the enemy so Granger can get kills easily
Watch Out For Faramis
100% counter win rate
Faramis's 2nd skill can affect the little gloo's from gloo's 2nd skill and burst gpoo down easily plus he can use his ultimate to save his teammates from gloo