Technology costumes: 

Notes from Dr. Bon

HACKER: this is an easy one. The public's perception of a hacker (per the existing videos, tv shows, etc.) would be someone in a dark hoodie and possibly wearing a mask like Mr. Robot. 

COMPUTER SCIENTIST/SOFTWARE ENGINEER/CYBERSECURITY: You could wear a suit to look business professional and dress it up with a nerd kit or a pixel bow tie.  Or, wear the floppy disk costume for a laugh!  A third option is to go full nerd!  Any academic-themed character is great with a nerd costume whether  your character's bio says you are a nerd or not :)  Velma is a nerd - so you could wear that and put on a spin that you're at a mystery party so you are channeling your inner Scooby-doo team to solve the case.

ROBOT/HUMANOID: There are a few options up there with robot costumes or you can just wear all silver and grab a robot mask.  Or even cheaper - wear all black (everyone probably has that in the closet) with the robot mask. Or, even more budget friendly is to wear all black and make your own robot mask by grabbing your next cardboard box that is shipped to your home. Cut out a window for your face. Paint it silver and decorate it with cut-out felt pieces.  Don't forget the cheesy antenna :)