Hello Craniak716!
While I have been playing
DF on and off for quite a while, I am more of a casual/small/scale player. Thus, I think I can give you some hints as to how to reduce the complexity of the game in the initial phase.
As was already mentioned, the init files are your friends, especially d_init.txt (in the data/init subdirectory). Besides the population settings mentioned by others, it also allows you to toggle features of the game.
Look for the following group of options:
[TEMPERATURE:YES]
[WEATHER:YES]
[ECONOMY:YES]
[INVADERS:NO]
[CAVEINS:YES]
[ARTIFACTS:YES]
[ZERO_RENT:NO]
Yours probably look a bit different, as this is my current version.
TEMPERATURE is important especially when you embark in extreme climates, but it also includes the risk of dwarves walking onto ice that melts under their feet in spring.
WEATHER is only a real problem in extreme climates (or evil biomes, I think), so I don't think it adds much to the core difficulty. In addition, you do need it for replenishing pools (which in themselves are not that important, though).
ECONOMY is currently completely deactivated, so this flag does nothing.
INVADERS is an important flag for difficulty for it sets whether any hostiles will enter your site. Mind you, wild animals are not counted as hostiles, so you can still have bears and tigers come around, but goblins and kobolds and the like can be stopped using this flag.
CAVEINS toggles whether unsupported parts of the fortress collapse. Given the oddities of digging habits of dwarves, accidents with caveins are a real threat in the beginning.
ARTIFACTS are a kind of bonus feature that may give you some exciting trinket in your fortress - or a potentially dangerously insane dwarf.
ZERO_RENT is related to ECONOMY and thus currently useless.
I recommend that you set all these features to NO initially, though WEATHER is not that important, I think.
Once you feel sure about the controls, you may turn on TEMPERATURE and CAVEINS (check carefully that you are not in for a bad surprise).
Once you have a feeling for creating goods, food, trading and the like, you may want to activate ARTIFACTS.
And once you feel comfortable with the game, you can turn on INVADERS to really get a new challenge.
As for the population cap, I personally recommend 7:
[POPULATION_CAP:7]
The game is hard coded to send an initial wave of migrants, regardless of your population cap, so you will end up with more than 7 dwarves. Mind you, with less than 20 dwarves, most things will take a while as you have a small work force, but without invaders, artifacts, extreme temperatures, and so on, you should have enough time to let your fortress grow slowly.
All these init settings can be changed during game play; or rather between game play sessions: Exit the game. Change set setting. Start and load the game. Some of the settings have a certain lag as some decisions in the game are made a while ahead of time.
If you had not created a world yet, I would have recommended the following course of action:
Design a world using advanced settings, select the MEDIUM REGION and press 'e' to edit the parameters.
Set the End Year to maybe 300.
Set Mineral Scarcity to 500. (This should give you lots of metals and gems you can work with)
Max out all the requirements for the titan attack. (This keeps trouble as far away as possible)
Set Vampire curses, werebeasts and secret types to 0. (This removes dangerous migrants which may mess up even a small fortress)
Set Levels Above Layer 1 to maybe 15 (This gives you enough room to learn before digging deeper into more difficult layers of the game)
Gen a world with those settings.
This way, some of the additional difficulties are removed from the game. The settings of the world you generated are permanent for that world, so if you have 0 vampires initially, you will never ever have any vampires in that particular world.
As for starting out, if you have invaders deactivated, you can safely farm above ground. This is extremely easy as all you need is to 'b'uild a few farm plots (maybe 2x2 each) on any space of sand, soil or grass (ignore the warning about water, that's for underground farming), then 'd'esignate a chunk of the map for 'p'lant gathering. The dwarves will harvest the marked bushes in that area, and once they have gathered any plants, you can tell your dwarves to plant those in the farm plots henceforth. This is probably the easiest and quickest way to start your farming industry.
These are my personal pieces of advice. Of course, keep the Wiki close by and feel free to ask the community here for help.
Yours,
Deathworks