I tried with Facebook and Instagram ads, and running giveaways, but nothing worked as expected.
Does anynone have any suggestion? I can invest on this (I paid for ads and giveaways prizes), but I'd like to try something new and not the same things that don't work.
1. Back then, it was common for related web sites to share links. So I started a links page that grew over time as I organized it into categories, all related to my subject. Then, I contacted all the other people who I was linking to and let them know, asking if they would link back to me. Most of the time, it worked and that's how I got initial traffic.
2. I submitted my site to search engines - any I could find.
3. I learned about SEO and started doing things that helped people find my content during a search. e.g. here's Google's page and there are many more resources out there: https://developers.google.com/search/docs. They also have free web tools to evaluate your site and make SEO recommendations. High quality content gets good rankings, but there are things you can do to make sure your content matches keywords that people search for.
4. I visited discussion forums on my site's subject and answered a lot of questions for people. In doing so, I added a signature to my posts that contained a URL to my site. Some forums won't allow signatures, but you can still put the URL in your profile. If you're good, some people will seek out your site and content.
5. I joined several social media sites. Any time I publish content, I post it on my social media sites. Some people in my line of work even curate high quality daily/weekly link lists and newsletters that drive a lot of traffic. When you search and find other people with the same interests, follow them. Many will check out your timeline and follow you back. After a while, you'll see content being increasingly tweeted, liked, and/or reposted.
6. I stumbled upon the concept of personal branding. Essentially, some people might start thinking about you as the go-to person for your subject. That's where recommendations come in.
These things take time. One of the things you'll want to do is watch your stats. After you do something, watch the stats for a while to see if that made it better. e.g. new visitors, feedback contacts, or search page rank for a set of keywords.