Here are a few suggestions you can try....
MASK--- (just in case you didnt know) when you buy a new mask you need to clean the oils off the glass. the best way to do that is to use a non abrasive toothpaste...a little water....and a finger. just put some toothpaste on the glass and rub it well. be sure to rinse it well or you will smell toothpaste a long time.
as far as defogger goes..... you can spit in it...and push it around with your fingers again
you can buy "professional" defoggers and use those....more finger pushing....
or, you can get a small squeeze bottle and put about 2/3 tap water and 1/3 no tears baby shampoo and that works like a champ. two advantages there.....no finger pushing....smells great !!
now that is the prep....as far as care goes....wash it very well in clean water as soon as you can right after a dive....especially if it is an ocean dive....you can dry slightly with a soft cotton cloth but most just let it air dry. personally, i never put any kind of preservative on the "rubber" parts.
as far as fins go....there is no particular prep after buying....but the same care after a dive. Clean as soon as you can with fresh water. I still would not coat the fins with anyting.
All dive gear should be stored out of direct sunlight and preferabley where it can get air. Not sealed up in a big plastic container.
Highly recommend getting some kind of carrier (back pack is cool) to carry your gear with while on vacation...or whatever...helps to keep it from getting lost. I also recommend marking your gear somehow....it all looks alike in a crowd.
one last item....when i go on an ocean dive...i keep two squirt top water bottles filled with fresh water in my pack. That way i can squirt my camera , dive computer, and my mask immediately with fresh water. Sure there are often "camera and mask" buckets on the boat...but by the time the second camera or mask hits the bucket it isnt fresh water any more.
good luck...!! hope this helped