Building your own wheels should get you exactly what you want. If you're building wheels for a 9 speed commuter, you're likely wasting your time since you can buy a wheelset cheaper than you can build from purchased components. If you have an out of production hub, obsolete spacing or gearing, or other needs, you can save a few bucks by learning how to do it yourself, or you can ask a builder/LBS to put it together for you for a one-off. At that point you're only learning a skill rather than paying for someone else's labor and (hopefully) a warranty on the labor.

I have only built 'simple' wheels; 32 or 36 spoke 3x cross using j bend spokes. I've learned a bit about the wheel as a system, which makes maintaining my wheels or fixing wheels simpler. The concepts aren't much different for straight pull spokes or lower cross # or lower spoke count wheels, it's just that the tools change and the margin for error decreases. If you go forward with building by yourself, remember to measure at least twice for your effective rim diameter, or where you expect the ends of the spokes to sit inside the rim once the hub is laced in. You'll find half a dozen methods to measure ERD here on the forum and elsewhere on the internet. Thankfully the spoke manufacturers have calculators so you don't have to question your recall of trigonometry to get to the right result.

An easy way to measure ERD is to take some old spokes of known length and nipples and find two holes opposite each other on the rim you plan to use. take the spokes and put one in each hole, then thread the nipple on so the spoke end is flush with the slot on the nipple. pull the spokes to the center of the rim and measure any gap or overlap with a pair of calipers. Your ERD is therefore the length of the spokes plus (or minus) the measured gap (overlap) between the heads of the spokes -~4mm (to account for the spoke thickness included when you measure this way). Make a few measurements around the rim to average and eliminate error from the rim being slightly ovalized. This method also works if the rim has a double wall and you can't directly access the spoke bed from outside the rim. If you have access to the spoke bed, you could use a stretchless tape or paper and wrap that around the rim at the spoke bed and measure the circumference, then divide by pi to get a diameter.