The fast offerings on the first Sunday of the month provide a local source of cash for the Bishop of each ward to assist families that are struggling to make ends meet. Often those families have unemployment problems. In exchange for that help, they often assist with simple tasks at the ward building e.g. vacuuming, dusting, tending to the landscaping. The Bishop can offer cash or send them down to the Bishop's Storehouse to pick up necessary groceries.
I hope your visit to the web pages provided some useful guidelines and resources. Being prepared is a constant process. If you keep doing a little bit, it isn't much of a burden to accomplish your objectives.
But I really had no idea of how much one might need for a family of 4, so the website was really helpful.