Get the elemental things down first:
Embark screen:
Jobs:At least one dedicated grower, who is possibly also a thresher (to process the harvested plants), dont let him do time consuming jobs at all - the better the grower the more yield the plots bring.
Another cook/brewer/grower combo to help him out makes a good team. Those two are practically the heart of the fortress; producing food, booze, threads for bags, syrup/flour/lavish meals for trading. If you could make beds and doors out of plump helmets you wouldnt need anyone else.
A mason to produce happiness improving furniture right away. One of the busiest dwarvers throughout the game. Doors as the simplest defence mechanisms, floodgates & hatches to control movement and flow of liquids, statues/cabinets/coffers to enhance room quality for happiness, stone blocks for bigger building projects - you name it. As with the grower give him some other jobs that only occur ever so often like trading or as medical dwarf.
A carpenter for beds, bins and barrels. Loses his significance once everyone has a bed and magma metal industry takes over the bin and barrel production, but early on you want these beds and barrels fast.
2+ miners to, obviously, mine out your future home in a timely fashion.
Another good idea is a mechanic: quickly setting up traps or a system to reliably divert water into your fortress can make a huge difference depending on starting situation; quality mechanisms also do very well for early trading (only bested by prepared meals and glass trap weaponry like corkscrews, etc.). A Miner/Mechanic is almost always one of my starting seven.
Items: Anvil, 2+ copper picks - as beginner, dont even think embarking without them.
One (female) cat to catch vermin.
2 dogs (female & male) for thief/snatcher detection, also do reasonably well for emergency food.
At least one rope (cave spider silk preferably as it is cheaper than pig tail) to chain a dog or construct a well.
A wooden training axe or better to chop down trees (yes you can chop wood with wood).
At least 20 plump helmet seeds; easiest plant to produce and process - every other plant has lower priority (11 seeds of each other kind is okay, dont bother about dimple seeds though).
Remaining points can be spent to your liking although I suggest bringing different kinds of meat and fish; for every different kind of meat/fish you get a free barrel.
After embarking:- safe storage for all your on embark brought stuff (dont want to lose the anvil to a monkey, do you?)
- a chained dog at the entrance to your fort as thief/snatcher detector surrounded by cage traps
- farming and brewing
- dormitory with 7-12 beds (roughly) and a good dining room
Your top plants should be plump helmets, sweet pods and cave wheat for usefullness and value (i.e. quality of your food). Sweet pods are processed into rum or dwarven sryup barrels by a thresher at a farmer's workshop and cave wheat results in beer or wheat flour when milled into bags at a quern by a miller. Having multiple sorts of alcohol or a lavishly prepared meal by a decent cook with all those ingredients can have a huge impact on your happiness which you shouldnt underestimate as a newbie who may make fatal mistakes in other areas.
I say again: happiness, Happiness,
MAGM- HAPPINESS. Unless you are really unlucky with ambushes or beasts a cage trap surrounded dog in your entrance will keep you safe. The only threat will come from within the fortress, namely food/happiness issues...
This should get you through the first year. When you get overwhelmed with the number of your dwarves and their job distribution I strongly suggest getting into Dwarf Therapist. You have the same editing abilities as in the in-game dwarf screen only with more helpful sorting options, batch job assignments and visibility => faster job management => more playtime. If it's not your thing, leave it, but other than being a fleshed out hardcore roguelike player, I see no reason not to use it.
After that:A wall with a raised bridge is impassable for groundbased enemies. You dont have to build the great wall of Mountainhome. Including some trees and grazing areas inside your perimeter is nice, but not ultimately a necessity. More traps also make for very easy defence against common enemies.
A vast dormitory for 60+ dwarves won't really cut it anymore; simple rooms ranging from 1x1 to 3x3 are well enough for non-nobles. Keep the apartments away from noise sources like workshops (in all 3 axes!).
For more effecient production don't just build a workshop next to a stockpile next to a stockpile and again next to another stockpile. It's a 3d game (well sort of). F.ex. stockpile the raw materials on z-level 0, build the processing workshops and maybe stockpiles for intermediate products a level below it and on z-level -2 store the end product. It looks neater, is faster and can help keeping everything on one screen.
General advice:Focus. Dont think about 'ooohh a waterfall in here would sure be nice' - get a maybe very spartan looking and minimal fort going first. A well organized mini fort can easily provide for 40+ dwarves with which you can achieve your future building goals faster and more efficient. Let the fortress grow.
And dont bother about aesthetics in your first few games. Keep it simple, keep it clear, keep your dwarves happy, keep it decently organized.
Once you can survive the first year routinely, you can go ahead and build those magma spewing colossal soap elephant wonders.
Take water seriously. If you are not certain whether your system of floodgates and hatches is enough to provide water without endangering your fort, build MORE OF THEM.
Also:
wiki. If you are overly confused by the game's many mechanics, jobs and items, look it up. What ores do you need to produce bronze, what pasture size does a yak need and how do you get from pig tail seeds to trousers? Noone can be expected to know all that right off the bat and while some take joy in finding these out by themselves, others do not.
One aspect of this game is that it has many aspects - dont be disappointed if you cannot grasp them all at once. You'll have to learn to crawl first before you can start walking.
But do yourself a favor and dont read any spoilers, there are some fun secrets in the game.
Of course all of these are advice coming from me; you dont have to follow them. The game comes with endless possibilities and even more ways to achieve them. Do what you want and see if you can go far enough with it. Dwarf Fortress poops all over so-called sandbox games in that regard.