When should you promote your books?

Today I came across a post on twitter saying that you shouldn't promote your first book until you have three or four released. I always thought that you were supposed to promote before you released anything, which is part of the reason that I started this blog. I was told that a good way to promote was to give reviewers free copies of my book and let them review it early, but the post that I read today said that you can waste time and money if you don't have multiple titles out. Both options make sense, but I'm not sure which will work better. Free feel to let me know your thoughts in the comments.