I'm looking at the requirements and I see that there are only 4 categories:
1- Employed 2 Self-employed 3- Retired 4- Student
I'm not any of them, what can I do?
Here's a link for example in Poland: https://www.schengenvisainfo.com/poland-visa/
Those categories are nowhere to be found in the relevant regulations and there is no requirement to be employed, self-employed, a student or retired as such. What is however required is being a bona fide visitor with sufficient financial means. The documents you would submit to establish that in turn depend on your situation, hence the distinction.
But if you don't fit any of these categories and yet can show you have a stable financial and personal situation, you should be fine too (I think the website you linked to hinted at this, under the somewhat confusing heading “if applicable”). For example, if you are taking care of your family but only your spouse has an income, you can provide documentation to that effect. Same thing if you are just wealthy and don't need to work.
Finally, if you are unemployed and without documented income, there is very little you can do. The requirements are designed to make it difficult for people like you to obtain a visa.
First look at the official site of Visa for Poland That is:
You have 2 types of Visa
Schengen C-type visa
The unified Schengen visa (C-type visa valid in Schengen states) entitles the holder to stay in the territory of all Schengen states.
National D-type visa
If you intend to stay in the territory of Poland for a total of more than 90 days (at least 91 days) during one or more visits within a half-year period calculated from the date of first entry, you need to apply for a national D-type visa.
More info about the types of Visa
What do you need to submitting for a C-type Schengen visa application?
The types and number of supplementary documents may differ depending on the consular office. In this connection we advise you to contact the relevant consulate to obtain full information concerning the documents needed when submitting a visa application.
What do you need to submitting for a D-type national visa application?
So you there is no difference between:
One tip always check official sites!
You may visit Schengen even when you do not belong in the 4 categories you mentioned above, if you have a relative in the EU and you intend to visit them, provided you can show that you are financially stable to support yourself during the entire stay, and that you intend to return back from the EU. For eg. if your daughter/son is settled in the EU, you may visit her/him.