Indeed eurorack and modular are some of the most addicting fun hobbies ever and the cutting edge of creative music world! I have been able to create the weirdest sounds that before were not as easy to do. Coming from a guitar and piano background, modular opens up millions of experimental options. Just watch that budget as it can be super expensive. I am trying to limit myself to my two 6U racks one of which is half full already the other completely full before spending another penny on gear.
Now for cables- I really like the longer Hosa eurorack patch cables they are solid so far but I did accidentally bend the end of one so always buy more than you think you need as you will run out after more complex patching! I like having a few stackable Tip Top audio cables so useful to use like passive mults which are key in a modular setup.
For brands, so far IME/Harvestman and Noise Engineering make the craziest wacked voice modules for many sound shaping options best suited for techno and industrial type stuff which I love. I like my core Doepfer modules they mix well with other brands and are solid built and sound decent as well. Intellijel makes good utility modules as does Mutable Instruments- love the Kinks and Links in my setup that Jim recommended to me a while back. While I do like the Richter Anti-Oscillator and Dual Borgh Filter a lot, the Malekko Quad Envelope and Varigate 4+ are trickier to figure out to do what I want in a sequencer and envelope generator. Plus Malekko support is sorely lacking! They don't even have manuals or solid documentation for a lot of their stuff!
Seriously, Malekko get your collective stuff together or I am never buying anymore of your gear!
On the other hand, folks at Intellijel, IME/Harvestman and Noise Engineering as well as Doepfer have been wonderful in answering my questions and technical issues right away when I had problems with their modules.