For must of us it is a commun and general tendency to select first a camera model and then combine an optic to it. After all it is the camera body that will register your picture and no picture mean no photography! Let say that is a bit similar to human nature with no possible image memory without a brain to sustain it. But think about the essential role that have to play your eyes during that process. Without them no image at all (except your own virtual in mind imagery of course...)
The different ILC camera systems will offer you a complete line-up of lenses. Some optics are more oriented to a general purpose use. Others are really specialized tools. The manufacturers will often produce a professional alternative of lenses that are designed for more intense use in adverse conditions. Moreover these "pro" optics are bigger units equipped with larger focusing and zooming rings, smoother mechanism, constant and larger maximum aperture for most of the models but these are also heavier devices to bring with you and operate.
Are you looking for focal fixed length or variable (zoom) ones? The price to pay for the zoom ones is usually a more modest maximum aperture and may be a variable one which can be annoying if you want to to keep constant your basic exposure parameters such as the shutter speed, the aperture or the ISO sensibility. The zoom (focal length) range is another factor to consider. All-in-one zoom models are addressing to photographs that like to work with a minimum photo equipment and a maximum of flexibility. The short zooms can be basic trans-standards optics or specialized ones like did trans-wide-angle or long telephoto models. The maximum optical quality will be obtained with the "pro" series and will be comparable to focal fixed (prime) lenses.
Give them a try!
So selecting a lens that will suit your need and taste can be a perilous exercice of pick so try and ... repeat again if necessary. The possibility to borrow them or to rent them or at least try them at the store or at manufacturer (store) clinics can help you. The other factor to consider is what will be the best camera combination to choose for the type of lens and the style of pictures you want to realize. Again trying the equipment will give an edge before buying the thing.
P.s. Lens Factor
If you intend to equip yourself with 2-3 or more different lenses chance you may adopt a complete lens system. The good way of doing it is to stay with the same manufacturer and the same lens model series. In doing so you are assuring yourself to have a fully comparable design, construction, optical results and future compatibility with the camera upgrades.