Positioning, map awareness, focuse and minion wave.
Positioning: are you in a dangerous position? Are you close enough to a teamate to be saved or save him?
Map: where is the enemy? Where are the escape routes? What buildables should be bought first?
Focuse: If an ally stuned, slowed, knocked up an enemy, join the fight 2vs1 is better. Dont lose focuse and try to work together. Chaining crowd control skills.
Minions: they are dangerous to your sentry or your grinder in meltdown, destroy them asap, you are miko? Well destroy those little bastards. They give exp and shards.
Those are the basics… Noobs usually lack 1 or more of them
Edit: forgot to add: lvls and death
Levels: you are getting behind? Maybe you cant kill all minions by yourself so try to dmg each of them to get shared exp. Help dmging enemy battleborns and buildables, If i remember correctly you have a window of 5 seconds to get shared exp. Build everything you can, doesnt matter if they get destroyed inmediatly, you get more exp from building than destroying. Buildables over gear, specially if you are getting behind.
Death: dont die, you give more exp to the enemy. Be a coward but dont stop pushing. Dont get in dangerous positions trying to secure a kill. If you dive in the enemy lines and kill 1 but the other 4 kill you, you just gave exp to 4 players and probably only you got the kill exp.