Signature campaigns on the forum can be just a piece of serious effective marketing campaign. Advertising in users signature space will help to gain some brand recognition rather than other guerillas direct marketing, which will bring a quick ^{and short} result.
OP also thinking about other forum and social media promotions. To be honest, most of the SM campaigns run here are worth nothing. Reposts or likes from fake SM accounts, do not bring a special result for the owner.

OP, before running any marketing campaign, you must first to do hard research and define a strategy. For now, you want a private discussion on PM or Discord, sounds like you want some advice for free.