Good and fun support, especially if combined with Xayah.
Abilities benefit from ap, going full ap will make you paper. Offtank ap items is an option. But we are focusing on helping adc/team, being an annoying CC-buff support.
Rakan as well as Xayah are weak vs poke/long range champions and CC of course.

Rakan is quite easy to master. Q & R very simple abilities. Only combo you can make is going in with W and going back with E, vice versa or E-W-E. While we are going in we are using our Q, to deal damage and heal ally when going back with E.
Combo example E-W-Q-E. E can only be used on ally champions, nothing other, can't be cast on self.

Laning vs another Rakan. You have to time your W and E in the right moment. Don't forget he can do everything just like you, go in-out with E and knock-up with W. So as soon as he uses E twice you can most likely knock him up. Not really sure, but from some games it seems the first Rakan to use W will lose that trade.

Don't forget to wait a little bit before re-using you E, when first shield is lost.

If you have any questions, feel free to comment. After playing some games, many ended up with an S- rank and a perfect or big KDA.