Best hero combinations for footmen?

There is no such thing. If there were, then the heroes would be labeled as: "This hero is good", "This one not so much" and "Use only if you don't have any other".

Every hero has their own pluses and minuses. If you're planning to have a legion entirely of footmen, look in hero's description (upper left corner in the hero's interface) and click that description for further details. Obviously, as the hero's level is increasing, so are their abilities (SX, SX1 and so on). Description of the hero will tell you where is he/she best suited, front, mid or back row. Place them according to that to maximise their abilities.

And yes, equipment makes a big difference, especially gold one.