how to go there from jiangxi? how much expenses for stay there 7 days for 2 persons?

Jiangxi is a province including many cities. Which city will you start from? As for the cost, it mainly depends on you, including your hotel budget, attraction route, dining and shopping, etc.

I'm at Ganzhou city..

The dining fare alone costs you CNY100-120 within 7 days on condition that you don't eat luxury food and eat local Chinese food. If you want to eat western food, you may cost about CNY 80 to 100 per day for two people.

As for the budget hostels, you may need CNY60-100 per night.