Ghostbusters World: What to do when out of traps?

In Ghostbusters World, what should you do when you run out of traps?

I know it's possible to buy more as an in-app purchase, but that's only a solution for a certain type of player, and should not be necessary in order to play the game.

I played the game for just one day, but upon running out of traps found myself stuck, not knowing how to proceed.

Surely there must be some strategy I am not aware of? (Web searches have been unfruitful.)

There are 2 ways I know of to get more traps:

1. Build more (this option is in the Character/Equipment menu, under the Traps tab)
2. Visit a gate (not every visit will give traps)

There may be others, such as daily/weekly challenges and leveling up.