I've been playing the same embark's first year for several times now, mostly to see how well I can do it. It was supposed to be a fairly simple embark -- military-oriented, with four dwarves being either military or metalworking and the wagon being mostly ore and coal. I wanted to have some metal armour in the first couple of years for once, and if I had to throw coal at the problem and skimp on a starting pick and axe to have enough points for skills and full sets of metal armour, well. I'm unlikely to be bothered by anything in the first year, and there's only one layer of aquifer on a cold map.
Turns out I forgot to bring stone, and while I can divert some of the flux to make into a kiln to get clay for more workshops (including a replacement kiln), it's not going to help me make mechanisms to make a bridge-dam for that major river going off the map. Oh, and I want enough room going through the aquifer to make a wagon-accessible spiral around the central borehole staircase.
Long story short, while I mostly manage to get things done with the jobs I have (the eat-drink-sleep cycle at the end of the second month is horrendous), I'm never happy with the results and go back to the embark numerous times, mostly before the year's out. All that time I usually get four immigrants with the first, maybe five, even if I manage to get a bunch of armour produced before they arrive. This time, I solve the problem by having pretty much everyone but the butcher doing the digging and furnacing. There's metal on-site, after all, I can spare those three chunks of malachite even though they were totally reserved for shields. The aquifer piercing goes quickly enough that I can use the ice to wall up the sides, the steel bars are made, and I get the three military dwarves training right at the start of summer (they seem to be much more efficient at teaching when they're in just their clothes. I have no idea why). Heck, I even find the time to make soap. Note to self: specialisation is nice, but sometimes throwing unskilled dwarves at things is nicer. So, with fortress wealth below 10,000 instead of the triple or quadruple that on the attempts where the armour got made, how many immigrants do I get in the first wave?
Seven. That might not seem very much, but having those extra two or three bodies when I'm essentially down three dwarves allows me to get some job specialisation going, get a dedicated cook, and start running a fortress instead of a hole in the ground that annoys the crap out of me and makes me want to go somewhere else.