Every game you have, no matter how bad it is, no matter how much people complain, just say "thanks, gg guys" after each one. Even if the other team just took you to the cleaners, there's literally no reason to say anything else. I used to try to give advice to newer people after matches, but some take offense to it so I only do so if specifically asked now.

There's a lot of things people don't realize...

1. There will always be new people, and the only way for those guys to improve is keep queuing and get experience. Everyone does this and you can't get upset at them for it.
2. The more people queuing, the faster your queues will be and the more pvp stuff we will get in the future
3. If you rage at people, you discourage them from queuing and are hurting PvP in the long term
4. There is often more going on than you see in the match (ex: You could be a dps and wonder why it seems like you're the only one attacking the healer. You don't see that the tank is peeling to help your healer, that your ranged is killing their melee, and that the only reason you were able to "solo" the healer was because their healer had to blow cooldowns to heal his melee).

Everyone is going to have frustrating matches, good thing you can just re-queue and get a new match, try not to let these guys get to you as in the long run they're just making themselves look bad.