You can use plastic bags over your base layer and under your sleeping socks and gloves. Safeway veggie bags. It may only add a little warmth but they are cheap and light, and who knows it might get colder than the "expected lows".
They do make Vapor Barrier clothing and bag liners. Maybe 5* pickup depending.
Don't breathe into your bag. Balaclavas help with that, and don't fall off your head while you sleep.
Borrow a fat pad or 2, it may be heavy but its worth it to have: one thermarest and one foam pad. Foam pad on bottom.
Sleep on dry ground. South faces may get quite warm during the day so look to camp there.
Sleep under a thick tree to exchange some radiant heat with it, rather than the great void. Shelter from the wind is also something to look for.
Lots of food. Hot water bottle. Try to sleep in between your buddies!