How to get first multiple entry Schengen visa

Question

I have 3 single visas in approximately 2 years.

Now I want to apply for MEV (multiple entry visa),
How Should I write my cover letter to ask for 1 year MEV?

What is more possibile duration that they will give me the MEV?

Answer 1

I want to apply for MEV (multiple entry visa), which country do you suggest? Netherlands or Spain? Or a new country?

Data on short-stay visas issued by Schengen countries for 2023 is available here and you can also view it by the country from which the applications were made (i.e., by consulate).

As others have commented, the way your question is phrased suggests that you might be visa shopping, which is frowned upon. I recommend you choose your destination based first on where you would most like to visit, and not on which looks like the easiest to get, in order to avoid giving a bad impression in your application.

How Should I write my cover letter to ask for 1 year MEV?

See How do I ask for a long validity Schengen visa?