This is a pretty broad question (and probably better suited for the ConTeXt mailing list), but I'll try to answer it the best I can.
In this mess I am figuring out a way to automate the design process: let the software impaginating the content; having the content provided as an external source (XML? Database?);
ConTeXt can typeset directly from a database, but there's much better support for typesetting from XML. Dealing with XML is a little tricky if you haven't done it before, but the manual is a pretty good reference. Depending on how exactly your data is stored, it may be easier to use another program (XSLT) to output ConTeXt code directly.
What's the problem? The documentation is huge and incomplete, I don't understand to what I should look into; from a "not so short introduction"
ConTeXt has some pretty good introductory material (ConTeXt an excursion and A not so short introduction) and some excellent advanced documentation, but I agree that there is a general lack of intermediate material.
This answer lists a few more resources. In general, I've had the best luck searching the Wiki or searching the mailing list archives. There's also the context tag on this website.
I also realized that I missed the newer ConTeXt LMXT.
Unless you're doing some fairly advanced or low-level stuff, you're unlikely to notice much difference between LMTX and MkIV, so I wouldn't worry too much about this for now.
I am a kind of person that prefer learning by doing, but I need to narrow down what I have know to make this project real
I'd first start by exporting 5 or so products to XML as a small test file. Then starting from the first section in the XML manual, you should be able to get a very basic ConTeXt file that simply prints all the items as plain, unformatted text. Then you can go back and add in some formatting to each item. To make the overall catalogue look good, you'll probably want to use columnsets to arrange the columns and layers to add some backgrounds. Then you can refine from there.
This would make my company willing to invest some resource in ConTeXt, maybe even contracting a developer, if I can demonstrate that we can work this way: better; safer; quicker; and using InDesign just for designing the covers and other stuff unrelated with the catalog production.
I use ConTeXt (and LaTeX sometimes) for nearly everything that I typeset since it nearly always gives better output than the alternatives, but if you're expecting to need a lot of outside help then you may want to stick with InDesign. Pragma ADE (the company that develops ConTeXt) offers contracting services, and there are a few other contractors too, but this doesn't compare to the tens of thousands of graphic designers who use InDesign. ConTeXt is one of the best options here, but it is still a fairly niche tool.
any reccomendations and suggestions will be very appreciated!
You can also consider using speedata publisher. It's unrelated to ConTeXt and I have no experience with it, but it is still TeX-based and open source, and it appears to be specifically designed for printing catalogues. But what you want should absolutely be possible to do with ConTeXt if that's what you want to use.
You'll also probably likely get some more answers if you post this same question to the ConTeXt mailing list.
