Citizen of Tonberry here and I think you'll find Tonberry to be the perfect server for you. It's about 50% english speaking players and 50% japanese players. Majority of the english players are from Australia and South East Asia while there are a small number of us from NA and EU. Also there are a number of large english FCs (300+ active members) such as Mirai (the fc I'm an officer in), Reven etc. If you're looking for a hard core FC that's focused on progression, then the number one progression FC on the server is LVN.

The only thing I have to warn you about is the fact that DF is mostly Japanese players. As we've been grouped into a Japanese Data center, you'll find yourself usually in DFs with Japanese players. PFs during prime time usually average about 20-30+ so it's quite an active server. Your biggest problem i think will be transferring in. You're gonna have to wait till server off peak hours to actually transfer in.

Hope this helped!