Of course the man cave is the focus here, but you want to be SURE Nobette doesn't feel slighted - the house is her domain, the man cave is yours (which makes all things right in the world - Nomex on ;-)
We built a small house (larger one in the works) but a large man cave - 50 by 90, 4,500 square feet (aircraft hangar and the world's second largest shoe closet - Imelda has us beat).
I didn't want to break the bank on the man cave because Dear Bride would have cut my throat. I was, however, able to do a creditable job anyway through stealth, craft, horse trading, etc.
Start with at least 70 amp service, 100 amps is better - and that's JUST for the garage.
Stop there with one or two outlets until you get your certificate of occupancy (and your building permit price may be partially based on the number of outlets you have), yeah, it's just a garage, I'll only have a single 60 watt bulb in it.
Once you are IN, then you can likely do whatever you darn well please without further "Imperial entanglements".
Outlets - quad outlet every eight feet along each side of the building. Electrical supplies bought from Garvin Industries, you have to BS them some and they'll set you up with a dealer account, whereupon the supplies are really inexpensive. Conduit comes from Home Depot (etc.), it is too long to ship economically. There are also LOTS of electrical supplies on Craigslist, but you need to know what you are looking for. Use 12 gauge wire, not 14 gauge, it costs a few cents more now, but if (when) you discover you need the extra capacity, it will already be there and you won't have to rip things out and start again. I have 220 volt outlets inside and outside, front and rear. If you have a compressor or a welder, you'll want 220 volts. Don't forget GFCI outlets at the feed for each outlet leg. You can't run fluorescent lights "downstream" of a GFCI, the starting surge trips the breaker. Fluorescents need their own feed.
Lights - I helped a local school remodel, and wound up with 24 fluorescent light fixtures, four bulbs each, 48" long. Free, drag 'em away. (Sure, no problem!) I replaced the old ballasts with high efficiency silent ballasts (eBay), and bought a case of bulbs (Google) from a company in Ohio. They had a $50 minimum for free freight, the shipping would have been about $45 more, so I bought ONE screwdriver for another $1.30 which put me over the $50 and they paid the freight.
They are in the east 2/3 of the hangar (which is where the workbenches are), and they are set up in four rows of six, wired so that I can turn on any group of three instead of lighting up the whole shebang all at once. For the west 1/3, I bought twelve egg warmer fixtures (Home Depot, these have 10" diameter aluminum reflectors) and installed high power CFL lamps. These are also wired in groups, I can turn on four, eight, or twelve, depending on what my lighting needs are. I don't need as much light on the west end because that's where the airplane is, and the airplane isn't afraid of the dark.
The conduit for the outlets is steel, this ensures no risk if I run something into it. The conduit for the overhead lights (up high where I can't damage it) is grey PVC, and it is assembled by friction fit, not glued, so if I have to revise anything, I can take it apart and put it back together with minimal fuss.
To determine what lighting you need, a short bit of research on Google will tell you how many lumens you need for any particular task. Storage doesn't take much, work areas take the most, pick your bulbs and layout accordingly. Err on the side of abundance, you cannot have too much light for intricate work. I'd rather risk sunburn ;-) than not be able to see what I'm doing.
Plumbing - when the slab was poured, I had six "L"s of 3" diameter PVC pipe in place before the concrete went in. This allows me to run pipes and wires into and out of the building without penetrating the walls or having to break up concrete. The inside ends are capped to prevent critters from living in the pipes or entering from the outside (we have field mice out here in the boonies, I do NOT want them taking up residence in the hangar), so far nothing has been able to chew through the PVC. Wire screens on the outside ends also help keep unwanted guests out.
Next up is a sink, parts washer, and a toilet. Hot water will come from a ten gallon "spot" water heater ($10 at the flea market), the sinks will be fiberglass laundry sinks - cheap and strong. Drain from the hand sink and toilet will go to the septic tank, I have not yet figured out what to do with oily water from the parts washer sink. (Back to Google, Florida hazmat regs say I don't make enough oily waste for them to bother with, but I don't want to just dump it on the ground.)
You'll want your light switches adjacent to the entry doors. This keeps you from having to stumble around in the dark garage and trip over things while you are groping for the light switch - don't laugh, I've seen it happen!
Final electrical notes, have photocell activated security lights over every entrance. (On at dusk, off at dawn.) If you use the new LED light bulbs, they use so little power that it will take a year to amortize the cost of the on-off switch!
Have a phone extension or two out there so you don't have to run into the house to be told you've won a Florida vacation . . . or if you need to ask someone a question or call for help. If you have a computer there, think about an RJ-45 connection, wireless may not work well.
On the inside, you cannot know the optimum layout for "stuff" until you've worked in there for a while. Visit Harbor Freight and buy a bunch of their $7.99 dollies (on sale). Scavenge the casters off some of them (you can't buy four casters for $8) and install them on some shipping pallets - that gives you a 1,000 pound capacity 36 by 40 dolly for less than a ten-spot. Put everything you can on wheels! That way when you have to re-arrange - and you will, more than once - it is just a matter of pushing stuff around instead of picking everything up, setting it aside, discovering it won't fit, then putting it all back again. ("I pick things up and I put them down.")
I scored half a dozen office style lateral filing cabinets at a thrift shop for $120 (they are $500 each, new). They are now on wheels (like everything else), and they are FULL of "stuff". So far, I have re-arranged probably four times, and it is no big deal at all, two hours work at most, half of that is just thinking about where they should go. I don't have to empty them to move them, I don't need a hand truck and risk a hernia (they are HEAVY, even empty, and they are NOT empty), just push.
If you set it up the way you like it, Nobette will always know exactly where to find you ;-)
Best,
Mike