Let's first list all the marketing options avaliable on bitcointalk. These are ranked by effective, in my opinion.

1. Bounty campaigns (paid in BTC/ETH of course), these usually include twitter, facebook and other campaigns which pay around 0.5-1$ per share/retweet or post/tweet. These are decent if you have a manager who can only accept users with active and not spammy twitter accounts. Without a good manager, I'd say this is the least effective way to market on the forum.

2. Ad space on bitcointalk. Follow this link - https://bitcointalk.org/index.php?topic=5137422.0

3. Signature campaigns.