Actually, you can successfully scry for the dwarven council member after you have recruited at least 5 other members, so he can be 6th or 7th.
Other than that the order doesn't matter, though the easiest ones to do would be Mage, lizard, human, and orc (who is very easy if you have already cleared the south east corner of Rivertown). The imp council quest is relatively short as well, though I left that one until last [<span class='standouttext'>Spoiler : </span><span class='spoiler'>to take best advantage of a jug there that gives you a level up.</span> (highlight the text to read)]. The end of the elf quest can be tough, so it would usually be better to do that as one of the last council quests.