Best backlink strategy with limited budget?

Hello,
Soon im starting my amazon niche journey with low KW competition and I have a budget of about 700$ to invest, in my country average salary unfortunately is about 300$ and i worked about 3 months between school years and ive managed to save up this much. What do you guys think is the most likely backlink strategy for this amount of money that will help me rank about 6 articles with 100/400 m/searches with decent on-page?
I might be asking the wrong questions because im kind of new to seo, if so let me know it will help me out allot.
Thanks

I always advice first timers against investing some money. There are plenty of ways to make money without investing (not that much but you can.). Try making youtube videos and ranking them on first position and see if it is making you money?

I am assuming your keyword is review type?

Or try writing content on web 20s and rank them higher.

Whatever you do try and make $50-$100 before you invest a single penny in that method. It can be done. Invest later.

If your keyword really is low comp, $700 is more than enough to rank it. You should be able to get to page 1 for less than $300 if you have a really easy keyword. Buy a niche relevant expired domain from @Nargil that has enough diversity and get a few decent PBN links/Guest Posts.

But this is only if you've manually checked your keyword to be low comp and not relied on tools.

Low competition keywords can be ranked quite easily. You can get your website ranked at a maximum investment upto $200 a month. You just need to work smartly or hire a prof. The choice is yours, PBN can help you rank easily but there is a risk too (specially for newbies). Setup your SEO work very carefully and make sure you do not go for such links that will spam your site ranking than helping you rank it.

Better you can try for Tumblr and web2.0 blog posts

Then you can try for PBN

Might be suitable for your solutions

One inexpensive way to build backlinks is by guest blogging. You can do it on your own if you are really on a budget. It just requires you time and decent amount of effort to execute it.