Using photogenic as an example:
to increase the Photogenic Club Skill to 48 the club will need to pay $280 000, 900 emeralds and 300 diamonds.
So that is the reason there is a Club cash box = to increase the club skills.
Only the president and vice-president is able to increase the skills.
If you hover over the skill, you'll see what it does for the club and how much it will cost to increase.