Just from glancing at your team there are 2 ways to increase your merchandise. Number 1 is you can win games. That can be difficult but the next 1 is more in your control. Make the majority or all of your team players from your nation. Merchandise does better with more players or all players from a team's home nation.
I have 1757 players for sale and I'm $25,835,360 in debt. Buy them at outrageous prices, or be selfish and make me go bankrupt. You decide, BB.