I second the recommendation for playing the steam version, mostly for the graphics, it makes the game easier to digest.
I like a few mods but there's really not any "necessary" mods. The biggest tool is DFHack, which can help you do some crazy cool things, but its by no means necessary, especially as a new player.
TIPS! spend some time in the first season getting a farm set up. Farms don't need to be too big, in fact if you make them huge you can run into a problem of every dwarf planting seeds constantly and nothing getting done. A couple plots with 9-10 tiles should be fine. A team of 7 dwarves drinks about 45 units of booze a season, to give you a rough idea of what you need.
Go into the labors menu, find the kitchen tab and designate all of your drinks as non-cookable. Dwarves can and will make roasts out of Just Wine if you let them ( ), this'll stop you from having an angry sober mob on your hands.
It's a good idea to have some sort of entrance that you can block off from the outside world. You can get some nasty visitors walking into your map unexpectedly, so you should be prepared. I like a bridge attached to a lever located somewhere well trafficked, like a panic button.
Dwarffortresswiki.org is your best friend, your faithful companion, any question you could possibly have will be answered there.
they're the same game, the only difference is that the steam version comes with a graphic tileset and UI, instead of ASCII characters. Everything else plays exactly the same!
The only mod I ever used was a tile-set mod to replace all the characters with images, and I didn't stick with it. After a while your brain gets all blurry for a second and you start just being able to see your fortress instead of little ds and ks moving around.
Everything's going to be super confusing for a while, and you're going to have FUN (dying horribly in bizarre and interesting ways) before you get the swing of things. The community motto is "Losing is fun". For most players it's less about building a successful fortress than it is building a fortress that explodes, disintegrates, and sinks in to lava in a novel or amusing way that makes for a good story. So frustration tolerance and an "oow what does this button do?" attitude help a lot.
I have many many hours in dwarf fortress and I agree with others here. Play the steam version. It even comes with a cute little tutorial.
Tips for a newbie are basically go into each fort knowing you will lose it but attempt to learn something new each time. Maybe the first time you learn how to dig and then everyone starves to death. Next time you already know how to dig so now maybe learn how to grow food and then everyone dies in a tantrum spiral because they don't have booze. That's okay next time you learn how to make booze and then you die to goblins. So next time you learn how the military works. Etc etc. That's kinda the FUN!
Or you can look up the dwarf fortress wiki and they have a really really solid new player article that basically explains how to setup a self sustainable fort from step one. You could just follow that guide and you'll do fine.
If you don't get the steam version, go for the easynewb pack mod set which the biggest QoL change is the ability to more easily manage the assigned job and skill system. That said, you will still die and things will still go horribly wrong, because you will pretty much always expand to a point that outstrips your capacity to produce without getting into incredibly dangerous areas. Either that or a noble will migrate in and completely fuck your economy.
As others here have suggested, if you go with the Steam edition you'll get a pretty new UI with mouse support and official tileset pre-installed among a variety of other QoL improvements (and some regressions that are being worked out, but nothing that will affect you having a good time.)
If you don't go with the Steam edition, I'd highly recommend getting started with the as it provides a nice launcher that allows you to change some internal settings and select from a handful of tilesets
First of all, Flinch already linked it, but I'll doubly recommend having the wiki open while you play. It's an invaluable resource, and anything you don't understand will be explained in detail there.
For your first fortress, I would personally try to settle somewhere without aquifers (although light aquifers are newer and pretty manageable), or you may get frustrated trying to deal with them while learning.
When you get settled in, have some workshops, bedrooms, etc., try checking out the basics of the nobles system, particularly managers and bookkeepers, early on. Having a manager will allow you to set up automatic tasks that are refreshed on certain conditions (i.e., Build 10 more beds IF number of beds in storage is less than 2.) Learning this early on will save you a lot of time and annoyance resubmitting tasks one-by-one for jobs that you would much rather have automated.
I could ramble about DF and little tips for hours, but honestly blind is the best thing to be when starting. Just be patient, use the wiki, and have fun!
spoiler
Oh, and if you dig really, really deep, you might find some delicious candy, or even a group of funny clowns, if you're lucky.