As the first step towards an inventory system order management would be where I would start. While I am an advocate of a full blown recipe based inventory system none of the ones I have seen and used (When to Manage) work in a way that is user friendly. I believe that it is possible but small steps first. We are using Simple Order which is a reasonable template but it isn't implemented as well as it could be.
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Let us know if there is a particular inventory solution you use and are happy with. Inventory would likely be an integration at this point, so we're looking to solicit feedback from our users on who they'd like that integration to be first and foremost.
Sorry Davis, I missed this post. We are using Simple Order.
You can also try EMERGE App, worked for both of our offline and online stores.