Futures lot size vs. my account size

What are the margin requirements for futures? What do they cost? If I have a small trading account and dedicate 25% to one person’s future trading system, how will that be executed with my broker if it’s a fractional unit?

You are asking two unrelated questions.

1) C2 uses industry-standard SPAN margins to determine the margin requirements you need to hold an open futures position.

2) If you AutoTrade a system, you can set your scaling at any percentage of the vendors. Thus, if the vendor trades 10 contracts and you have 20% scaling, you will trade 2 contracts. If the same vendor trades 1 contract, you will not trade 0.2 contracts, since of course that is impossible. C2 rounds up to at least one contract in these cases.