I am not a Reddit guy specialist, but from general forum activity I would suppose building engagement or karma first would be better, especially for building better reception of your eventual posts. How about pursuing both, where you do commenting then later evolve into posting? Or, creatively combine the two, as in first read several new posts with comments relevant to your niche, then write a useful post without links spelling out your take on the topic?
After which, you go back to the new posts/comments, and write comments (with link) pointing to your main post, and your money page outside Reddit. "Oh, by the way, I went into this subject more fully over here (Reddit link), based on this (off Reddit link)." The latter may even be respectably disguised, e.g., as a Wikipedia page or YouTube video/channel about your site. Your main content is protected by the 'innocent' post, and comments on it by you that get removed can be replaced by new ones.