You will have to obtain links to your site if you want to rank. Usually you’d pay for those.
There are some other ways but they aren’t easy nor are they time effective. In other words you are going to put in lots of work if you don’t want to pay.
Here are your options:
1. Link bait content
Basically content written for other writers and webmasters, containing usefull resources like statistics and such that would make them want to link to you.
2. Outreach
You will have to reach out (via email usually) to other site owners and ask them to either link to your site or give you the possibility to do a guest post.
Look into outreach tactics like broken link building and others.
That’s pretty much it. You could also network with other site owners in many ways, including in person and build connections in your industry that will put you in the position of easily obtaining links.
Good luck.