I'd agree with the other answers here that in the beginning, your best bet will be to leverage the audience of your guests.

There's a trick to doing it properly. Instead of just sending them a link to tweet or letting them know when the episode is live, it's important to make it dead simple for them to share.

You can create sound bites and upload it to Soundcloud and it'll play directly in the twitter feed. You can create custom graphics for them to share on social media. Get creative here.

Another thing you can do is launch a giveaway to promote the podcast. Entry couldbe something like subscribing and leaving a comment on a specific episode.

Some podcast platforms (see more here: https://www.kyleads.com/blog/podcast-hosting/) also have built in directories that help distribute your podcast further.

You may even consider using cheap social ads to build up that engagement and social proof. Social ads paired with a landing page (see more here: https://www.kyleads.com/learn/landing-pages/builder-software/) that focuses on either capturing email subscribers or podcast subscriptions would be a good investment. You want to try to get over that initial hump of about 1,000 regular listeners.

From there you may start to see compounding effects.

Hope this helps.