A lot of the basic information that applies to the usage of OAT also applies to the OpenAstroExplorer. So you might find some repeated information here.
More general information can also be found in the Astrophotography, Astrophoto Setup
While there isnt a general answer ala "Buy X, get pretty space pictures", the next best answer is: The best gear is the one you already have. Pretty much every DSLR made in the last 15 years will suffice. Even a kit lens will be okay for starting out, although a bad lens is much worse than a old camera. If you want to get a new lens, check out used vintage lenses.
If you want to delve into proper telescopes, detailed information about those would take too much space here. As the OAE functions no different to other commercial telescope mount, the information you can learn on the internet will also be applicable here. But if I have to leave you with one tip: Bigger isn't always better.
While OAT could function somewhat standalone, OAE can not. As of now, i can not be controlled without some computer, preferably a windows machine.
You probably came across the term "Autoguiding". But what is it and whats the benefits?
An Autoguider is a extra camera and scope with high magnification. It uses a PC to watch the position of a single star and if that star moves slightly it will issue a correction to the mounts motors.
This significantly increases the possible focal length and exposure time that can be achieved with OAE, while also increasing the amount of usable images without star trails.
You may take a look at the OpenAstroGuider.
See the Software and OATControl pages.
See the Guiding page.