Google claims to have more than 200 ranking factors in its search engine algorithm. That makes it incredibly hard to know which things are important and how important. But really we can boil a site's success down to TWO things - the quality of its content and how many other websites link to it.
When your site has 30 pages of content (or so) your focus will switch from adding new articles to getting more links.
But even at this early stage where you have a blank site, or just a few blog posts and a contact page, you can start thinking about linkbuilding (i.e. getting links) and networking (i.e. shmoozing up to important people in the niche).
It's helpful to join forums etc early (i.e. before your site is anywhere near ready) - part of your reputation in those groups is how long you've been a member.
1. Blog Commenting
Find blogs in your niche. Search using this kind of pattern:
food blog "1 comment"
food blog "2 comments"
to quickly find sites where you can leave comments. Change the date on the search to only show RECENT articles.
Read the article, leave an interesting comment. Don't just go 'top article bro!' Try to add some value.
In the name/website field of the comment section you can link back to your site. You might want to vary the name you use. If I leave a comment I just use Andrew, but if I wanted to position myself as a niche site mentor I could put my name as 'Andrew the Niche Site Mentor'.
You WILL get people clicking through the link to your site over time, and it's really worth taking an hour a week to leave these comments. You'll also get to know your niche MUCH better, so it's win-win.
Oh, and if you ever want to write a guest post for that blog, it'll be easier if they recognise you as someone who contributes to the discussion a lot. So track what blogs you interact with on a Google Doc or Excel file.
2. Relevant Forums
You can type 'keyword + forum' and hopefully find forums where people discuss your topic. You can include the link to your site in your profile and signature, which is nice.
Don't start spamming the forum with your site. 'Lurk' for a while to get the feel for the place. If you find an opportunity to comment, praise, ask a question - go for it. But there's no need to overdo it.
Basically our goal is to join a forum and leave about 20 comments over the first 6 months. That way, when you start dropping messages like 'oh that's a good question, the answer is in this article I wrote' nobody will get mad at you. (Avoid linking to 'money' pages - people on the forum will resent that. But linking to helpful informational articles will be appreciated.)
3. Facebook Groups
Similar to joining a forum, and possibly more active these days. Do a search for your keyword, join a few groups. As before, don't link to your own site until you have something great to show them, and give more than you take.
Depending on your niche, Reddit can be a good place to be. As always, lurk for a while before posting. They will be vicious if they think you are just there to dump your links.