Factors to consider while buying beginner audiophile IEM:
Fit - IEMs can either go straight or over-the-ear. Straight IEMs are designed with cables hanging straight down, while over-ear IEMs have cables that wrap over the back of the ears. Choosing either of these types comes down to taste and preferences.
Drivers - IEMs use drivers to reproduce sound. These miniaturised driver components are like the ones used in full-size headphones but smaller. The drivers in IEMs include dynamic, balanced armature, planar magnetic, electrostatic, and hybrid drivers. All these drivers come with their lists of pros and cons.
Cables - Some In-ear monitors will come with removable or detachable cables that let you upgrade, or change them in case of any accidents. Some IEMs come with a fixed cable, which is not removable by design.
Connectors/Termination - In the case of In-Ears with detachable cables, it is helpful to understand the termination used. IEMs can offer connectivity via an MMCX (micro-miniature coaxial) connector or a 2-Pin connector.
Tuning - This is a clear indicator of the capability of the IEM to reproduce frequencies and tones in the audible spectrum. There are numerous ways an IEM can be tuned, and knowing the tuning of an IEM can help you make an informed decision.