Hi, welcome here

!
First question, on which server do you play ?
Because on the subs one it will be very hard to pop the 3v3s and battlegrounds, because there is a lack of players.
For the F2P, Bgs always pop except on the CET night. For the 3v3s, some days it pop, some days not. It's because people sign only when there is timer on the queue. And the queue appear only when there is people signed, so it's a vicious circle. But when it pop, there is differents team, which you will fight 3 times maximum on the day.
You will easily see that there always the same good party signed at the 700+ points and some randomn or boosters behind them.
Gl and HF btw !