Well, it depends a lot! The main cast thinks romance in different ways:
Nadhine is a bit touchy on those matters; she's not so good at showing her feelings. However, for her beloved, male or female alike, she would do something simple, yet meaningful, like a stroll on Azoria's orchads near the oasis, or even forging him/her a jewelry or an ornated weaponry (she's a blacksmith xD)
Esther is the opposite of Nadhine; a romantic through and through, she would plan the perfect date for her husband, Yami, from sunrise to sunset, cooking nice meals, finding some cozy spots to hang out and finishing the day on the terrace, watching the sunset with a picnic set.
Yami is a hardworking man who takes everything seriously, including his love for his wife Esther; he would surprise her with small, meaningful details from sunrise to sunset, sweeping her off her feet at any chances he would have, bring her flowers, jewelry and her favourite treats as well!
Raheem, being a Djinn, sees things through another looking glass; for him, music is the key to showing romance, and he would bend the winds to his will just for them to recite a poem or even sing a song in multiple voices for his beloved to hear. However, he doesn't grasp the concept of romance very well xD