I had a bunch of spreadsheets when I first started - for inventory, purchases, sales, shipping, taxes.
I found an inventory program that actually maintains all that information for me - including outside etsy orders. All I do is create an order if I sell something outside the etsy site. The really nice thing is that etsy listings/fees/status can be imported so you don't have to duplicate efforts there.
It's called craftybase. You should check it out.
full disclosure: they don't pay me to be happy with their service, but if you do decide to sign up and use my referral code, we'll both get a discount.
http://craftybase.com/ref/938e46b5