It's not fast, but you can make more money by doing three/four things a day. So to start Pick Flowers, then Work Overtime in the shop, that brings you up to Night. Sell flowers if at or above average, keep if not, then go to the princess to spend time with her and get paid for it.
You just have to make the most of each day. But it still takes a while to build up depending on how much money you had left over when you get the new Contract offer