Startup {1-of-3}   /scoreboard objectives add money dummy (The name you want to be displayed)

Startup {2-of-3}   /scoreboard objectives setdisplay sidebar money

Startup {3-of-3}  /scoreboard players set @p money 1

Adding And Removing Currency

/scoreboard players add @p money {}

/scoreboard players remove @p money {}

Minimum money check: /testfor @p[score_money_min=]