If you're on a thrifty mission, your best bet is this Topshop Tank. It's a wonderful product, while not very costly. Another strong contender for your wardrobe is this Caroline Rose Tank. While the price of this item is rather reasonable, it will certainly attract a lot of attention. You might also want to consider this J.Crew Tank. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.
If you're looking for a happy medium, look at this Caroline Rose Tank. While the price is very reasonable, this piece is an easy wardrobe update. It's also worth checking out this Misook Tank. This piece is extremely popular and, just as importantly, not too pricey. Alternatively, opting for this Neiman Marcus Tank is a good choice as well!
If you want to splurge, then you won't be disappointed if you check out this Lafayette 148 New York Tank. It's a costly but smart option. While you're at it, also have a look at this Derek Lam Tank. Yes, this item is expensive, but it does not mean it's not worth it. In this price range, you can also take a look at this Helmut Lang Tank. You won't regret the money spent!