Let's flip this around, trader comes to you and he has taken a few trades in Crude Oil since June 2014 and he has taken his $3,000 account to $63,000 and he wants you to give him $15,000 to manage and trade other markets like Meats and Lumber, whacha think? He says he stayed at a Holiday Inn one night and read few books.
Percentages means little unless you have years at it and many trades. Most don't know Larry Williams who turned $10k into over a million had several accounts going and I believe he has ran it up pretty good amount and was in bad drawdown by end of the year.
Just too risky for anyone to feel comfy to give you any money at this time.