If you're budget-restricted, your best bet is this Joan Vass Tank. It's a popular piece, while not very expensive. Another good option is this Nic+Zoe Tank. While the price is not too high, be sure that this product will become a wonderful addition to your wardrobe. You may also want to look at this Caroline Rose Tank. This item is not expensive either, but it will make a difference in your wardrobe.
If you're looking for a happy medium, consider this Misook Tank. While the price is very reasonable, this item is an easy wardrobe update. It's also worth looking at this Current/Elliott Tank. This piece is ultra popular and, just as importantly, not too pricey. Alternatively, opting for this Joan Vass Tank is a great choice as well!
If you want to treat yourself, then you absolutely must check out this The Row Tank. This item seems pricey, but it's well worth it. While you're at it, also have a look at this M Missoni Tank. Yes, this item is expensive, but it does not mean it's not worth it. Also take a look at this Caroline Rose Tank. You won't regret the money spent!