I don't think you should purchase tether honestly. It has a lot of fishy behavior behind it and the team. If you must use it, just use it to temporarily offset drops in BTC or ETH and buy back in. There's no point in holding tether and honestly I'd consider it dangerous to say the least.
Tether is the biggest stable coin in the cryptocurrency market at the moment, and I think only USDT is worth to buy in all stablecoins. So that you should use it to avoid losing the money when the market goes down the next time.