How many keywords can I put in my page for google spiders ?
If you speak about meta keywords: 0
Take much care about the content of your
<title> tag, all the words you use in the headings tags (
<h2>, ...), and the quality of the content of your page.
You can also have a lot of precious guidance here:
G. Qyy is right, meta keywords are useless in today's SEO world.
In terms of targeting content for search engines, I'm a bit old school and like single-focused keyword targeting. Now, Google will likely - over time - find a cluster of keywords but as you're writing I'd think about just one or potentially two terms (if it's a modifier.)
So, if you're writing about a Purple Cheetah, then that should be the keyword target, but you might also target Fast Purple Cheetah.
While writing good content can sometimes work, there are plenty of examples where that fails. So I recommend writing for search engines.
It's actually about writing good web content - which will benefit human and bot readers alike.