Strength Training can be an important part of a training plan. Some runners swear by it, others not so much (me). You don’t need to be a member of a gym to do strength work, there are lots of body weight exercises that can help you get stronger.
Make sure you are doing the exercises correctly as bad form and posture can have a detrimental effect and even cause injuries rather than prevent them. Try to work on your own areas of weakness to become a better all round athlete.