What do you mean by chain? You can do batch commands where you put everything together and have them run in a specific order. i.e.
Text file commands.txt contains:
gam create user ....
gam create user ....
commit-batch
gam update user ...
gam update group <> add manager user <>
Then the command:
gam batch .\commands.txt
This will use multiple processes/threads to create the users simultaneously, but it won't run the next set of commands until everything above commit-batch has been completed.
Note that I use gamadv-xtd3 for everything. I don't recall if it's available in Jay's GAM.
If you have an example of what you're trying to accomplish, I can try to be more help.