How to select domain name

I have a e-shop and i have made a blog for it. And now i am writing some articles on it.

I was thinking of buying some domains for my keywords. My keyword is 2 words XXX XXX the domain xxxxxxx.tld is taken but the xxx-xxx.tld is free
is it still ok SEO-vise to take it and redirect it to the blogpost? And then build links to that domain? Or does it not matter? I don't want the blog to have the domain just that post so i was thinking of redirect and build links to the new key-worded domain. BAD or GOOD?

What is best practice? I am trying to learn SEO so this is a small experiment am doing the keyword itself is easy ranked 1.200 searches a month.
Not to high competitive.

First: having and EMD is not mandatory, you have to be careful not to get overoptimization when using an EMD.
Second: using a hyphen in the domain name won't have any negative influence

Is there suck thing as over optimisation ? I didn't hear of it, could you elaborate please ?

Thank you!

What would you think about my tactics?

My main domain where i host my e-shop and also the blog on is one domain its semi related to my keyword.
But for the blogpost only and linkbuilding i will do to the domain with the keyword in it. Is this a good tactic to redirect via that domain?
Or is it better to use the domain name and make a micro blog only on the keywords topic?

Choosing a domain name is similar to choosing a company name it requires a lot of thought and consideration. Below are the things that you should consider
1. Make it Easy to Type
2. Keep it Short
3. Use Keywords
4. Target Your Area
5. Avoid Numbers and Hyphens
6. Be Memorable
7. Research It
8. Use an Appropriate Domain Name Extension
9. Protect and Build Your Brand
10. Act Fast

Hyphens are a no go, it divides your domain up and could cause some consumers to forget about the URL.