It all depends on what you want to do with your store and the level you are selling and marketing. For the small stores that are just hobbies then doing things manually is probably the best way.
When your store is doing $10k, $20k, $30k+ a month then you seriously don't want to be doing ANYTHING manually.
I'd advise doing things manually and saving your money until you have sales to support an app. Word to the wise...if you are going to spend money, spend it on driving traffic.