What is the main staple food ofin Spain?

You do not have to stay "main staple food". Staple already implies you are talking about food.

In Spain the main staple foodt is paella.

There are different kinds of this dishpaella, but my favourite is made with seafood.

"Favorite" is also an acceptable spelling.

The main ingredients are rice, lemons (or lemon juice), peas, chicken, prawns, clams, mussels and squids.

I do not think squid has a plural.

The best place to eat this staple food ispaella is in Valencia.

I highly recommend that you to eat seafood paella in a bar, near the coast.

Generally when you write a sentence like this, you should support your recommendation with facts. For example, is it because the seafood is fresher near the coast? or is it because the ambiance at a bar is better than at a restaurant? is it because bars generally hire better chefs?

It will be an experience that you won't ever forget ever.

What iIs the mMain sStaple fFood of Spain?

In English, the first letter of all nouns, verbs, pronouns, adverbs, etc., are capitalized in the title.

In Spain, the main staple food is paella.

There are different kindvariations of this dish, but my favourite is made with seafood.

I don’t think that “kinds” was wrong, but I felt as if “variations” was more natural here.

The main ingredients are rice, lemon, peas, chicken, prawns, clams, mussels, and squids.

I highly recommend that you to eat seafood paella in a bar, near the coast.

It will be an experience that you won't’ll never forget ever.