how to know my dps is good enough?

Answer 1

if you're able to kill stuff(characters, not bosses) around your level at a decent speed then it's good enough

Answer 2

If you're playing WOW you can download mods which tell you your DPS and then you can compare to people around your level.

 

It's really hard to tell what you're asking though. To get a better answer, try asking 'how to know if my dps in ______ is good enough to _____.