There are numerous ways to sum up the teachings. In the Pali Canon you can find many suttas where the Buddha is asked to give a brief instruction. They are generally insufficient for people with no knowledge of Buddhism. Therefore, there is what is called gradual instruction
, that the Dhammapada quote above covers.Don't do evil, do good
: Dana (generosity), Sila (virtue)
Result: Sagga (heaven)Tame the mind
: Adinava (drawbacks), Nekkhamma (renunciation)
Path and result: Four Noble Truths
If you want something less complicated, you can use the concept of "interbeing" or "dependent origination" as the cardinal doctrine of Buddhism. It is the best of you pick something that you can elaborate on if required. It doesn't matter if it's about ethics, meditation or wisdom, since all of them are connected to the other parts.
"While teachers of the middle way, mind only, transcendent wisdom, mantra, and other schools may have their own assertions, the fulfillment of those intentions is the same. There is not a single thing that is not contained within mind."
(Gampopa to Düsum Khyenpa, in "The First Karmapa", KTD Pub, p254)
“If you recognize the world of appearance and existence as the mind, realize the mind itself as empty, and have no grasping at the superiority of your realizations — this is the ultimate view."
(Chegom Dzongpa, in "The Book of Kadam", Wisdom Pub, p609)