Do blow your own trumpet.
To create a successful business, it's generally best to let people know you're in business. Few become noteworthy when kept quiet, especially when the enterprise in question is selling things like greeting cards.
These days you need an “online presence”, which basically means shouting about yourself relentlessly on social media and hashtagging the shit out of everything you say... #followme #nothatscalledstalking. And if shameless self-promotion doesn't come naturally to you, you kinda have to suck it up and do it anyway.
Nope – posting a photo on Instagram every 6 weeks is not being relentless. Setting up a Twitter and not using it is counterproductive to your cause. And being too stubborn to have a business Facebook page is at best moronic. So learn to embrace talking about yourself like everybody cares. Apparently a fair few people do. But anyway, even if they don't, you've always got the support of your best friends...