It used to be $100, since the micro futures where released it is $25.
It looks like they do need to change their website because at the top it says $100 and when you scroll down it says $25.
Anyway, i had a chat with them last week and they confirmed it is $25.
Edit: minimum deposit for AMP Global (Europe) is $100, minimum deposit for AMP Futures (US) is $25.
I was able to open an account with only $100 years ago only to see exchange real time volumes. Perhaps this can still be true. TradingView supports only CQG. I recommend Sierra Chart with Rithmic feed. It's great and the cost is very cheap.