You should only recruit heroes with at least one stat of 60 or higher.
The level of the hero is irrelevant. Only the statistics matter. A level 15 hero with a highest stat of 45 is worth less than a level 2 hero with a 62 in one stat. In fact you pay for heroes based on their level so a low level hero with high stats is preferred.
Politics helps with building your city and gathering resources.
Intelligence helps with spying and research in your academy.
Attack helps with fighting battles and defending your city.