Should I get backlinks only to one single page?

Well, my website is ranking on Google quite low. The home page is ranking well, but the other pages are from 10 to 50. I picked up a single page (not homepage) which is ranking 10-30 and started buying guest posts with backlinks on this page. The guest posts are from high-quality but not niche-relevant domains (however, articles are relevant, of course). Now I want to check if there are any improvements with the rank of this page.

The question is, is this a good strategy to try getting backlinks only to one single page?
Do I also have to buy links to other pages? I just don't want to waste money.

Share with me your experience. Thank you.

first, make homepage authority than go for other pages

From what I've been reading a more "natural" backlink profile will have links to not just your home page but also to other pages within the site. For example, a news/blog site (like CNN/Fox/BBC/etc.) is going to a lot of links to their main page, but will also have articles directly linked as well. Just like Walmart will have links to their home page and some will also link to individual products.

That's what I've been doing.

I should make a home-page (user-friendly and also Google friendly) and then I would make another page apart to link it.