E-commerce infrastructure for supplier / manufacturer

Hi, I'm new here in the forum, so let me know if I'm posted in the wrong area.

I work for a wholesale company and manufacturer of fine jewelry in the United States. For the past 2 years, we have been developing our e-commerce business, as it has proven to be a viable sales channel for us.

What we do is simple. We have thousands of SKUs that we store in our office. We also manufacture new products abroad. These products are listed in a variety of sites. We sell through Amazon, Amazon FBA, Overstock, Fingerhut, Groupon, Jcpenny, Sears.com, etc …

Our problem is that our current infrastructure is not compatible with this type of business. We manage to survive with emergency solutions, but ultimately, our wholesale business operations can not adapt to the different operational requirements of electronic commerce. E.g. Amazon has many fees and our accounting and ERP software was not designed to accurately track and analyze all of this. Another example would be our catalog. I've had to build this from scratch using excel, have an internal internal in all the possible details of the product, but it's getting to the point where I can not efficiently track or implement skus on all channels. I started using Ragic, which until now is fine, but I have not tested it completely.

So, my question is, could I, how would I build an infrastructure if I could start from scratch for this type of business?

That is to say. using Xero for accounting, a2x for incredible reconciliation, stitchlabs / channeladvisor for channel management, aws for image link hosting, etc.

* note: I must also bear in mind the costs, since I do not have a large budget to work with. Ideally, I would like to create my own system, but for now I think I would have to work with the addition of different tools.
SEMrush

Thanks in advance!