There are a few different ways to answer this question, and it really depends on what you mean by best. If you're looking for the most versatile palette that will allow you to create a wide range of looks, then I would recommend the Urban Decay Naked Palette. It comes with 12 neutral eyeshadows in a mix of matte and shimmer finishes, plus a double-sided brush. This palette is great for beginners because it includes everything you need to create both simple everyday looks and more dramatic evening looks.
If you're looking for the best quality eyeshadows, then I would recommend the Make Up For Ever Artist Palette. It comes with 16 high-pigment shadows in a mix of matte and shimmer finishes. The shadows in this palette are incredibly easy to work with, so it's perfect for beginners who want to create beautiful eye makeup looks without any fuss.
Finally, if you're on a budget but still want decent quality eyeshadows, I would recommend the e.l.f. Studio 14 Pieceeyeshadow Palette. It comes with 14 highly pigmented shadows in a mix of matte and shimmer finishes, plus 4 bonus eyeliners. The shadows in this palette are very easy to blend, making it ideal for beginner makeup users who want to create professional-looking eye makeup without spending a lot of money.