Resaerch:
Mining, Bronze working, then required only neccessary worker (hunting, husbandry, wheel, farming, pottery), military (archery, possibly iron working) or religious techs. The reason for or is that you want to research metal casing ASAP, chop or poprush forges in all your cities, employ engineers. Next step is organized religion or theocracy (25% for buildings or units). I usually find organised religion best.