you need to weigh your items and measure your packaging, then go to usps.com and use their shipping price calculator. Use the farthest zip code you can find from your own location (try several) and set your shipping cost as the highest result you get to cover your bases. You can offer to refund overages, but remember to cover your packaging/handling expenses within your shipping cost so you don't end up losing money (or add packaging costs to your listing price).
we really can't give you an answer without knowing ANYTHING about the items you're shipping. you can either follow the usps.com suggestions we've given you, OR search etsy for similar items to yours and see what common shipping prices are. You will need to do SOME leg work, there's no uniform answer we can give you here.