There are a lot of factors affecting the number of spectators that will come to your stadium:
- Your league layer: The higher you play, the more fans will come
- Your reputation: The higher, the better
- The match type: Fans are much more interested in important matches. They are most interested in relegation matches, followed by regular league matches. Friendly matches are a lot less popular. In the cup and International Masters more fans will come the farther you get.
- Your stadium level: The more you expand your stadium, the higher the stadium level will get, and the more fans will come.
- The number of popular players: Popular players draw more fans into the stadium
- The ticket prices: The higher you set the prices, the fewer fans will be willing to pay them.
- Stadium capacity, parking and public transportation: Obviously, there will never be more fans than you have seats in the stadium and parking spots or public transportation capacity.
- Stadium upgrades, Spectator plus (rare & common): You can get 10% more spectators if you have Spectator plus (rare) stadium upgrade activated, or 5% more spectators if you have Spectator plus (common) stadium upgrade. These two activated at the same time will give you 15% more spectators in your home matches.
To maximize your income, you will probably have to keep playing around a bit with your ticket prices to find the right balance of ticket price and visitor numbers.
However, the ticket revenues are not everything. The more fans there are in your stadium, the higher the home field advantage will be. So especially in important matches it might be a good idea to lower the ticket price to give yourself the edge over the other team. Also, the more fans come to your stadium, the more money you can earn from gastronomy.
United matches are always played on neutral ground. There are no ticket revenues or home field advantage.