I think the first thing you need to ask yourself is how do you plan on selling your items. will you have an online shop, sell at festivals are you trying to do wholesale.You also may want to consider the cost of letterpress dies, paper, envelopes and packaging supplies this may also help dictate how much you are going to print at once.If your only going to sell online, it can sometimes take awhile to start getting traffic to your site so you may not need to print as many up front. Also if you are just starting out you may want to start off with a couple of designs and test them out before investing to much in a style or color that may not be as popular as you thought.When I first started off I created a bunch of stuff and I just new folks were going to love it all. Since I have always sold primarily at festivals I was able to get feedback that you don’t always get online. While a lot of it was popular I picked up valuable info from the customers and was able to figure out cards and saying that people were looking for.I’m sure this does not really answer your question, but I hope it helps you figure out what you think will work for you