In the US I use calculated shipping. Apparently this is not available in all countries. With calculated, you set up all the box sizes you use. Then you measure and weigh each item with the bubblewrap or whatever you pad with, but without the box. Etsy should then combine the weights and select the smallest size box you have listed that the total order will fit in and give you the price, based on zip code and how far the customer is from you. It works most of the time within a few cents, but occasionally, I will have an item (mostly beads) that tends to overcharge when there are a lot of strands, and I have to do a partial refund. But at least I don't have to go back and ask the customer for more money.
On foreign orders you don't have to figure out a rate for each country since their zip code is used so it does it automatically.
The other way to do it is to charge a flat rate no matter where the customer lives, plus an additional amount for each additional item, like $5.00 for the first item and $2.00 for each additional item, or whatever numbers you need. In this method you will need to charge for the customers that are furthest from you and you will be overcharging customers who live closer to you. Or you can figure out the amount for mid range distances, then you will gain a bit on closer orders and lose a bit on orders further away, but over time it should average out.
For foreign orders, you will have to figure out a rate for each individual foreign country you ship to.
