You may get a job in a small charter company with just a Commercial Licence however you will give yourself a much better chance for Airline selection if you have an Instrument Rating.
All of your training through to Commercial Pilot Licence is in a single engine aeroplane using Visual Flight Rules (this means you navigate by reference to the ground and that you cannot fly through cloud). As you would be aware, airlines do not fly by visual flight- they make their flight plans and conduct their flight according to Instrument Flight Rules (IFR).
If you have conducted instrument training and can fly a multi engine aircraft, the airline will be much more likely to consider you for an interview.
