Instrumental music-especially one with calm tones and a medium or slower tempo (speed). Sometimes picking music outside of what you might consider meditation music is fun. For instance tropical beats or Arabic pop that's instrumental might change your practice. There are great playlists out there for yoga and meditation but also searching 'instrumental' in front of anything might surprise you! Words in music might distract too much for a casual meditator. You might find that opening your window and letting the natural sounds around you in is also pleasant for your practice.
As for subject to meditate on: problems or decisions that are upcoming in your life, how you feel about certain subjects (observe thoughts but do not try to engage them), why a situation is the way it is, or even doing an observation meditation of an object or an experience (such as being outside).
Experiment and take time to see what works for you and you might find success where you never thought to look for it. Reading a little about meditation might also give you more ideas
Ocean waves, it reminds me of sitting on the beach early in the morning when no one is around and everything is calm and peaceful