I don’t know much about online advertising and I don’t know where to begin, that’s the problem. I’ve researched a bit, but from what I can see the advice is usually “pay someone to do it for you” or something like that. I don’t want to do paid internet ads or anything like that for two reasons:
As the other posts have mentioned, more details would be useful to give tailored advice.
However, you have a slight misconception of online advertising. Although in some cases you buy "space", similar to a billboard, generally you don't. Instead, you buy "clicks", regardless how many times your ad has actually shown. Having a specific niche is actually perfect for online advertising. You can generally tailor who even sees your ad based on the characteristics of your niche, and can tailor the text/content of the ad to only appeal to your niche.
In such a case, you can have a extremely good cost per acquisition, although maturing the campaign (finding the correct settings and text to filter out the "noise" clicks) can make your first month or so more expensive than after.
It's this initial start up and fine tuning phase that is generally what people recommend having hired out. Google and other advertising mediums can get really, really expensive if you leave it at the default "buckshot" mode or let Google do the optimizing itself (the house always wins). Once that's done, agencies will then go into a maintenance mode where they review and curate your ads once every month (or week, depending), which may not be necessary if you're willing to learn to interpret the results yourself.
(1) my business is small and specialized so I only need to reach my niche audience, and I don’t need that much customers at the beginning (I’m starting slowly since this is my first business)
Depending on the niche, the actual cost of the clicks can be as low as $0.05 - $0.15 each, or up to several dollars. The former is quite a small price to pay considering the only people
seeing your ad are those that fit your demographics, and those
clicking your ad and triggering a cost are those that not only fit your demographic and search terms, but also agreed with your ad's text. By the time you've paid and they've visited your site they're already a high potential customer.
As well, you can turn off the ads at any point if you acquire enough customers; you don't keep paying after you don't need them.
(2) I don’t have any money to spend on advertising, and even if I did I’m sure there are better, more Mustachian ways to do it without spending a lot of money!
The internet is a tough place to start. You can try pushing your existing network towards your new site/business, but without existing credibility it takes a very long time to accrue relevant site visitors organically.
But, like I’ve said, I’m at a loss here. Except for some general ideas like advertising on forums etc. and the usual word of mouth I don’t know where to start. Buying ad space is a bad call for sure, and I have limited experience with SEO strategies.
Those general ideas are about it; but also keep in mind a lot of forums and communities have issues with "spamming" your business if you're not a known member (again, without an existing network, it's hard).
Be careful with anything SEO: most of the content out there is very parasitic; based around trying to "game" the search engines to increase your rankings. If it costs money, don't do it. If someone uses questionable methods in regards to your website, you run the risk of Google detecting it and delisting you (e.g. your site disappears entirely from Google search results).
SEO is a complete topic unto itself, but there are a few top things to remember about it:
1. Good, clear, semantic web coding. Google
sees your site entirely based on the code within it, so make sure it's done in line with standard web practices.
2. Original content. The more original content on a site, the better regarded by Google. This generally means to create a blog and talk about topics within your niche.
3. Links. Google uses links as proxies to rate the worth of your site. If something like CNN (a well regarded, highly cited site) links to you, some of CNN's reputation rubs off on you. This is the cause for a lot of spam in comments, forums, etc. This is also what most "SEO"people sell (links), and is also what will get you
banned from Google. If Google decides that the proliferation of links to your site is unnatural or paid, they will ban you with little recourse.