Now I have two steam account, bombess and bombless. I received a dota2 account invite email and click the link I received when I was using my steam account bombess. So now bombess got the gift. But I actually want to play dota2 with the account bombless. What can I do now? Do I have to play with my account bombess now or is it possible to tranfer that invite to my bombless steam account?
Yes it is possible to transfer gifts (in case you haven't activated them by mistake).
Now you can also use the steam trade offers in case you have issues with direct gifting.
There are 2 ways to do it:
The first one described by Arremer:
The Second one (faster but require 2 computers):