7Wonders Duel is one of our favorite strategy games, unfortunately it is not completely balanced. The first player has the advantage to start in the first era as well as the third era. The second player starts only in the second era. (Of course, this doesn’t hold when one player gets a military advantage)
This is not only unfair because the second player starts less often; it is also less good to start in the second era than it is to start in the first era. If you take the first card in the second era, you always open another card, which is not the case in the first era.
Fortunately it is really easy to introduce a new rule to make 7Wonders Duel a more fair and balanced game. This rule is that the first player starts out with only five gold coins instead of seven. Five is a good amount, because it is too little to buy two yellow, commercial cards that cost three each.