i think the minimum amout to iinvest in forex is depend on the lot you trade.if instaforex you trade 0.01 lot, so perpips would be 0,01 usd, if you hace money 5usd, you have power until 500 pips, i think that is ideal........the problem some people want to get more so with a little money they use big lot.and sometime got MC. and i think you must spend about 500 money as investment to business with amount 8 money because you must determine the variety of pips the industry shift it if it opposite on you so you need big investment to not reduce it quick but to fill the opposite.