If you have had many jobs, describe the positives. You were gaining experience and useful skills; you travelled and gained cross-cultural experience, etc. Relate your experience to the position that you are applying for.
Here is an example answer for a well-travelled ESL teacher:
My object of research as well as my interest and hobby is cross-cultural communication. I like travelling and I want to learn about cultures, traditions and languages of the world. The best way of studying another culture is living and working among people of that particular culture and learning from the local people. Travelling and learning about the world gave me an excellent opportunity to grow academically and professionally.