Can I just sign up for Krisflyer membership?

Membership signup is free - that should be good and easy for you, Additionally, I would sign up for a couple of cards if I was you to maximize the sign up bonuses

https://www.singaporeair.com/en_UK/ppsclub-kris...

You can sign up even if you use a cashback card.

You earn miles when you fly on revenue tickets. Why let it go to waste?

Your citi reward card earn points that can be used for miles.

(Since you have citibank credit card, go for Citibank Premiermiles card, it is my default choice as the miles does not expire).

Yes miles card are more worth than cashback for big expenses as many cashback cards have limits on cashbacks (Need to spend $x for 3 months etc etc). So miles are better for big item spending.

You can sign up for Krisflyer anytime with or without credit card. Go for the Citibank Premiermiles and you can get a krisflyer together with it.

I'd say it's indeed worth to sign up for a miles card considering you have a big expense coming up in the foreseeable future. As most cashbacks cards have a limit to the cashback per month per category, miles solves this issue by eliminating such a cap. You may also consider applying for cards with miles that do not expire such as DBS Altitude and Citi PremierMiles.

Do also make full use of the sign-up bonueses which can be very attractive and you shouldn't have any issues meeting them with the upcoming wedding expense. There are usually many promotions in the market, I would recommend staying up to date with all the sign-up bonus that are on offer, especially to new-to-bank customers. You can keep track of them either via:

• SingSaver or MoneySmart. They regularly share sign-up bonus from the various banks, say $250 for signing up for a Citibank card as a new-to-bank customer.

• Milelion Roar telegram broadcast channel (https://t.me/milelionroars). They post all (I think?) promotions almost in real time, as well as compile a Weekly Deal Summary to ensure you do not miss out on any promotion. Best of all, it is a channel so no spams! Only the best stuff shared there

Apply for these cards nearing to the actual payment date, as most qualifying period for the sign up bonus are for expenses within the first 3-6 months.

All the best!