Will be doing a super cheap MR staying at HIX Kowloon East 20k points (no other similiar hotels available)

I plan on taking bus there E22A from airport. Not sure if Octopus card is worth it, since I will buy dinner on credit card and don't really see much to spend on.

So, how do you pay on a bus? is exact fare required or is there a fare card?

I have been to HK once before, so no need to sightsee.

THANKS