Every time you use the /dream or !dream commands your request is added to the queue for processing. Your commands will be processed in the order they are added.
The queueing system will not process all your individual requests in direct sequential order though. It will alternate between users in the queue so that each user gets inputs back quicker vs. someone that loads lots of requests into the queue at once.
There are currently no limits on usage for holders. If Pixie Bolt AI gets too clogged, we may consider setting a limit per day/week.