Winning the game even on chieftain difficulty may be quite difficult for players who have not played before or haven't played enough to learn the greater strategies of the game. From the beginning of civilization, no nation ever did well without conflict and conquering lands.
In the game, including all civilization games one to three, if you are to win by conquering the lands, betrayal "must" be taken into account, with a city that is gracious or polite towards you, after agreeing to a right of passage, move a large army towards their capital city.
Note: With a rival of yours give offer them a luxury of which they do not have, then ask them per turn, as many numbers as you can fit in, whatever billion gold per turn. This is a quick way of earning high gold, with this high amount of gold, you can get them to offer you every one of their cities except their capital, then you destroy them.
If there are other rivals on the map, with your great amount of gold, you can get them to form a military alliance with you.
Remember, the greatest mistake is taking your cities into account before the safety of your people, a great military is 100% better than a great wonder or city, if you know that you can conquer the world, then you know you can conquer the height of your cities.