In the beginning it's better to do one or two things really well than many things poorly. Part of that is finding places where you can leverage tools and software to free up time to focus on growing the business.
Don't try to take on too much at once. All those apps took me months to get running. Now the site practically runs itself! I went from one package through USPS to over 2500 a week. If it can happen to me, it can happen to you.
Starting with zero background in e-commerce, we've been able to start from scratch with Shopify, and build a profitable business that we're proud of.
Marketing begins with product design. Unless you have a truly unique product, it will be very hard to differentiate and gain brand traction, especially online.
I wasted a couple of months by delaying our launch so that I could make everything "perfect." The truth is there will always be something that could be better or more compelling, don't use that as an excuse.