This is old but I just came across this thread and I am familiar with Gemini. You may have figured it out or probably went another route by now - but, for anyone else trying Gemini: The first transaction is wire transfer. After that goes through, you can use ACH. It's a security measure that it's your bank acct.
I personally like the Gemini platform due to the privacy culture. BTC purchases are a tiny higher than average but transfers to hardware or other BTC addresses are free.