I remember that someone had posted a thread some time ago about doing a full peaceful run in Ireland. Furthermore he wanted to unite the island of Ireland without a single war being fought there (even AI against AI). From what I remember he almost managed but at one point one AI nation declared against another.
So I think it is definitely possible to have a run with only minimum outright conquest.
I would personally start somewhere with a lot of minors and far away from all the big bullies that might bring war to your doorstep (like Rome, Diadochi, Carthage etc). Ireland & Scotland seem the best bets as they have both a lot of minors and not so many large neighbours. Engalnd & Germany could also work although the tags are larger there. An added bonus for these areas is that you will have more to do there as you won't be fighting. Changing to a monarchy or republic, building cities and roads, colonising can all be in your to do list!