It's possible to win without aid requests. You can get: 7 points from wonders; 2 points from the tech/civic trees; 8-10 points from pre-modern congresses (before the diplo vote is available). How many congresses you will get before the modern era vary depending on the difficulty. On deity, you'll get 4 congresses, on immortal you will get 4 in most games, but you might still get 5, on emperor or lower you'll get 5 (I'm not sure if it's possible to get 6 on lower difficulties); 5 points from the first post-modern congress. So you can get up to 22 points by the first post-modern congress on higher difficulties without aid requests, 24 on lower difficulties (30 turns later, though). On lower difficulties, you can win even if the AI all vote against you in the diplo vote (10+7+2+1), but you can't afford to lose even a single point. On higher difficulties, you need to prevent the AI from voting against you, so you can win the diplo vote. You accomplish that by delaying the construction of the Statue of Liberty into the diplo vote, so you don't trigger the AI into thinking you're winning. If you do that, you can lose two points and still win. If you delay the statue of liberty in lower difficulties, you can lose 4 points and still win. You can skip the statue entirely if you don't lose any point.