Go IMC first, then Night.
Unless you're going to fly a twin regularly then forget it. Twin currency is 10 'sectors' a year (a sector being depart, 15 minutes minimum in the cruise, and arrival) plus an annual sign off flight. This is the bare minimum and it's barely enough to stay safe. A twin is twice as safe if you're up to speed - and twice as deadly if you're not. Also it'll cost you double the money (at least) in aircraft hire but you won't get double the speed.
So - IMC. Possibly, providing the tuition is good, the most useful 15 hours you will ever do (unless you get a full Instrument rating). Rating is valid for 25 months, re-tested by two approaches plus partial panel and full panel flying with an examiner. It'll make your flying more accurate, and enable you to fly on those 'marginal' days when you wouldn't. You'll also get the best view in flying - on top of clouds rather than beneath them.
Night Qualification - 5 hours flying, some solo. Once you get it the problem is going to be using it unless you operate from an airport that operates decent hours. Nice to have, and useable, especially in winter.
Remember this before you decide which one to do first - you can't see clouds at night until you're inside them, by which time it's too late and you'll find yourself saying "I wish I'd done the IMC first" or you'll be saying "I'm glad I did the IMC first"
P.S - Justiciar and I obviously crossed. But one thing to correct in his post is the multi is
not type specific.