I know this is an old thread, but it may be helpful for other people. I've also put brackets in to show the charge and to avoid confusion.
So you know the reaction between (C2O4)2-) and (MnO4-) is:
16(H+) + 2(MnO4-) + 5(C2O4)2-) => 2(Mn)2+) + 10(CO2) + 8H20
And you know the reaction between (Fe)2+) and (MnO4-) is
8(H+) + (MnO4-) + 5(Fe)2+) => (Mn)2+) + 5(Fe)3+) + 4H20
You need Fe and C2O4 in a 1:1 ratio because of FeC2O4nH20 (Fe and C2O4 react in equal moles) and in the equations above, there are 5 moles of both, so they are already in a 1:1 ratio.
So you just have to add both equations, to get:
24(H+) + 3(MnO4-) + 5(C2O4)2-) + 5(Fe)2+) = 3(Mn)2+) + 10CO2 + 5(Fe)3+) + 12H2O
As 5 moles of (Fe)2+) and (C2O4)2-) react with 3 moles of (MnO4-), the ratio of (Fe)2+) & (C2O2)2-) to (MnO4-) is 5:3, which simplifies to 1 : 0.6