Getting all future emails from a sender to appear in the “Primary” tab (instead of “Promotions”, or elsewhere) is a quick, two-step process. First of all, drag-and-drop the email message from beneath the tab it’s currently filed under, to the “Primary” tab.
Once done, a message alert will appear with, “This conversation has been moved to Primary. Do this for all future messages from [email protected]?”. Select “Yes”.
Gmail on mobile devices doesn’t provide a way to prioritize messages. However, touching “Show images”, then “Always show images from Sender” will ensure that images always display in the inbox.