hey wilson and welcome
last year was my first year duck hunting, but iv learn some valuable things:
#1-cant be 2 warm. it gets a little cold here in nc so you want to be warm, some days it got to like 9 degrees,brrrr...so if you can use some of you dads warm hunting jackets...thats what i did. thermal underwear is also a good idea to wear and since you hunt on the coast you probably want some waders. i got friends that got 2 pair, one for the early season when its still a little warm and one for when i gets cold, but you dont NEED two...i only got one. when or if you get waders make sure they have enough insultation, my freinds have anywhere between 1000 and 1600 gram insultation, mine is 1000 and i like them, it all depends on how cold it gets. good socks are also good to wear under the waders so make sure you buy waders big enough for some thick socks.
#2- get a facemask and good gloves. you will need to be pretty covered up so the ducks wont see you. you want to pair of gloves, one thin pair and one thick pair, for when it warm and when it cold
another good thing to have is to get some good shells. there are plenty of posts on shotshells, but you might want to buy some and try them out to see how they pattern.
i hope this helps you somehow