I think the #webcomic tag is perfect for your main tag. That seems to be the place for serial action/adventure webcomics like yours.

Since you're posting original webcomics, you should also consider the #comics and #steem-cartoon tags. They're very popular and active. If you have any questions about the #steem-cartoon tag, ask the co-founders @perennial and @sireh. They're very friendly and helpful.

At one point, @bryan-imhoff created a project called Steem Comic Convention, #steemcomiccon, to promote comics like yours. It looks like it's inactive but Mr. Imhoff has been around longer than I have and might have better advice for promoting your style of comic on Steemit. I'd introduce myself on this thread:
https://steemit.com/steemcomiccon/@steem-comic-con/introduce-yourself-to-the-steem-comic-convention

If you include your drawing process in a post (sketches, inking, coloring, etc.), you could probably get attention using the #art and #drawing tags.

Check out the comments in this post by @jackpurcell38 for more advice.
https://steemit.com/batman/@jackpurcell38/what-is-the-most-interesting-aspect-to-see