The easiest song ever: “Lady in Black” by the Uriah Heap
The second easiest song ever: “You Never Can Tell” by Chuck Berry
Both can be played using only 2 chords. Once you learn them, you can move on to basic 3-chord rock n’ roll tunes (your run-of-the-mill Presleys will do fine) and folk songs, Dylan ballads etc. Stick to strumming for now, arpeggios are tougher and I’d leave them for later, once your left hand is ready.