@Marge010 I wouldn't call myself a good player. There are far better players than me who would easily shred me if you gave them a P2020 and no body shield.
But even as a non-caustic player - or rather as someone who hasn't set Caustic as his main character - the common mistake I see is that players like to rely on their gas a bit too much. It's not a standalone ability, and is like any other ability in this game preferably treated as utility at most. Is provides area denial, but a good player will still go through your gas and likely down at least one person.
Treat the Caustic gas as a way to surprise players, rather than using it offensively or too defensively. Have the traps already set in places that you believe will be advantageous. If you happen to get into combat, you can lure them to chase you into your already prepared building. And before you know it, they go a bit too quickly into the house, become susceptible to attacks and if you want to make this extra funny, just leave an arc grenade on their body.
Also, keep in mind, ultimate accelerants exist. Have at least one with you at all times, and you can get ready for an ambush even if your ultimate isn't ready YET.
