If you write in a particular genre, that genre usually has conventions. The conventions can range from a small local one of a couple thousand people to tens of thousands (San Diego Comic Con).
Newer authors might not be able to afford a table at a con, but there are ways you can market your work without having to sell physical copies.
Author cards: They’re like business cards, but they have your website and socials printed on them, usually with your book cover or logo.
Bookmarks: What do readers can never have enough of? Bookmarks! This is where branding comes in, but get creative. Book covers on bookmarks aren’t the only way to sell your books. You could simply have a scene from your book with a QR code leading to where you sell your books. Even if they lose the bookmark, they’ll have your sales site in their phones.
Thinking of making your own business cards and/or bookmark? No problem. Canva has printing templates and prints for you for a fee, shipping the swag directly to your home or to the convention itself. There are plenty of websites that will generate QR codes to lead to your sales sites for free.