You can get cheaper K+DCAN Cables (the cable which connects Laptop USB port to Vehicle OBD II Socket), but BimmerGeeks Pro Cable for $45 is a tested & trusted product, so you can spend your time learning how to use INPA (Factory-Level BMW Diagnostic Software), NCS (Coding Software), BOTH in BMW Standard Tools, and ISTA+ (Rheingold, BMW Dealer-Level Diagnostic Software) which is BOTH Diagnostic Software and Reference Documents for:
1) Wiring Diagrams, with interactive "Installation Locations" and "Connector Views";
2) Repair Operations; Procedures for removal & replacement of components;
3) Functional Descriptions -- How a System or Component works;
4) Torque Specs, and MORE.
EVERYTHING you will need to Maintain, Diagnose & Repair your E9x is in one of those "Tools". ALL may be downloaded free from the MEGA sites linked in the attached pdf: "E9x References", which also contains links to Bentley Manual, RealOEM.com Parts Catalog, BMW Owner Registration and Recall Status sites, etc. I also attach "INPA Quickstart Tutorial" which offers suggestions on how to get started using INPA, and contains some sample screens.
There is so much Detail and functionality in the Software, you could spend days/weeks learning the basics of how to use it. Start small, learn how to read and clear fault codes in ALL ~ 20 Modules in your vehicle, and how to "Connect" to the primary Modules such as the DME, CAS, FRM & DSC, so you can view "Live Data" perform "Activations" of motors & solenoids, and read Fault Details & Freeze Frame Data.
There is a growing number of folks on the Forum who are learning more about INPA/ISTA, and the more participants with the SAME software, the more we all can learn from each other.
George