You can put 100’s of keywords on a single page, there is no limit to the overall number of keywords that you can use on a page. However, you are not going to be writing pages, based on a specific number of keywords, instead, what you should be doing is to come up with the main keywords that the webpage is about.
For example: you have a website about car insurance, your keywords could be car insurance, auto insurance, however, if you’re writing an article about “car Insurance” and what’s the best way to find car insurance, and how to get it at an affordable rate, you are likely to hundreds of keywords.
The moment you make your post thorough, which is the most important step, the more thorough your content when you have 2000+ word blog post, you will naturally include long tail keywords.
If you’re writing a post about car insurance, you will naturally speak about over paying, or under paying, how to find a good deal, what terms are good, what terms are bad, which providers you should be looking for, and which you should not look at.
To get ranked for hundreds of keywords you should:
Focus only a few keywords, and write thorough content surrounding the topic you have chosen.
If you have done this correctly, you will write an amazing thorough article focusing on 2 – 4 keywords, and will naturally rank for hundreds of long tail phrases. This will naturally happen, users search for long tail phrases, and as you write thorough content you will naturally include these phrases in your content.