How to make perfect butter cream?

Please could someone give me ratios for butter to icing for:

Good pipeable buttercream

AND

Good spreadable buttercream

I have seen buttercream on many YouTube channels and it always looks so smooth and creamy and mine just seems to be so hard to spread and it's a bit too loose for piping. I just don't know what to do. Please could I get a recipe and advice? I am aware buttercream isn't just butter and icing sugar please feel free to let me know if I'm missing ingredients.

Look forward to hearing from you.

I would prefer to hear from people who actually bake rather than just someone finding a link for me. Please only post a link if you have actually used the recipe and can guarantee it works.

Thanks