I'm surprised by your 1, because when I read mail in gnus, they are marked read in gmail.
For the rest, gmail maps labels to IMAP folder, so
B m nnimap+gmail:commande
Will move the article to the commande label, and mark it with the commande label. GNUS will create the folder if needed.
Probably, copying the mail with B c
will add the label, but I don't use it.
B m nnimap+gmail:[Gmail]/Trash
will put it into the trash folder, and so delete it.
Deleting it with B Del
or using expiry (E
) will just remove the label or archive the message. I've setup:
(setq gnus-parameters
'(("nnimap\\+gmail:INBOX" (expiry-wait . 2))))
This will archive message marked for expiry two day after they have been received.