If you want to use a popular hashtag for visibility, a good go-to would be #grownostr. This hashtag was created to encourage non-Bitcoin related content, so literally anything that is not about Bitcoin would be relevant.
Discussion
To be honest I would feel bad adding this hashtag to a marketing post. Doesn't look appropriate for me.
Visibility, not marketing. Trying to sell something? Use hashtags related to what you are selling.
Grownostr is for posts that aren't about Bitcoin, like gardening, hiking, or literally any other topic folks might be interested in.
The idea is to go to the grownostr hashtag if you want to find new people to follow, not stuff to buy.