How to extract a series of letters following a symbol

I have a series of scraped tweets from Twitter relating to different projects. I am looking to find the date of the first time they mention each project. The project is identified as $ followed by a series of letters. For example $LINK or $ETH.

The two steps of this process that I can see (yet have been unable to achieve is),

a) extract the '$...' from each tweet (for instance $LINK)
b) filter the data to only show the first occurrence a project is tweeted.

Here is an example bit of the data.

https://docs.google.com/spreadsheets/d/1wcf-dCoK7akLRmFbgAFyNT-8TwTwcLaoxEZtYMnY7tA/edit?usp=sharing

Any assistance would be greatly appreciated.