In the variant section you can find several homemade 2-player rules.
Have not tried any of them so cant comment on which to use. I love 7 wonders but think it fails to deliver as a 2 player. So many better 2 player games I would rather spend my time on.
(If you want a meaty 2 player I would suggest to check out Martin Wallave new game "A few acres of snow" - it is absolutely brilliant)
You do need a fake third player to keep the balance of things.
I really like my variant:
Setup the game like a normal 3 player game and give the "third" player a board and 3 coins and the usual hand of cards.
On the dummys turn a random card is drawn from it's hand.
It tries to build that card first. If it it can't, then tries to buy resources from trade.
If it really can't then it tries to build the stages of it's wonder.
If it can't do that either, then it discards the card for 3 coins.
When trading it opts to buy cheapest resources first and then it tries to balance who it gives money too. Roll a die or flip a coin if you have to. But generally it was very logical who it would pay.
Why do I prefer my variant over the built in 2 player variant?
1) we don't have to decide something for the third player and hence the game is faster.
2) it seems more realistic/natural/balanced. Our scores are usually rather close when we use my variant. When we tried the official variant I was nearly 20 points ahead of my wife.
3) it was less confusing because it felt like I was playing a normal 3 player game.