I had a good experience on Huobi.pro. After opening an account, I was able to send 1 DASH token, convert it to their USDT and then buy THETA. This took me about 10 minutes. They made me wait 24 hours to withdraw since it was my first transaction, and charged me 10 THETA, about $2.21 as a transfer fee. The THETA appeared in my Myetherwallet in a few minutes. They do require multiple confirmations with google authenticator code, email code, and sms code which are annoying but do-able.
by
139B085,7 March 2018
Source: www.cryptocompare.com