You don't have to fly Emirates 3 times a year to get a free frequent flyer account. You earn points (= miles) for tickets flown, which you can later redeem for free tickets, upgrades to business class or higher status in the programme.
Register with Emirates and present your number with each booking.
For just one return ticket, you should be able to get a free ticket with easyJet, which is a partner of this programme.
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