If this is your first autocross, I'd worry more about smoothness and overall strategy. Just get comfortable with the car and the process. Your first event is part of a longer learning process.
If you feel slightly out-of-control at the start (due to a sudden launch), it could be tough to settle down for the rest of the run. A moderately fast start will be fine and allow you to "take in" more about the overall course.
For example, some larger autocross courses will allow you to "apex" the various turns. But if you run a course laid out in a smaller parking lot, it may be best to simply take the path of shortest distance rather than worry about an ideal apex location. It'll be easier to figure this out if you don't focus too much on having a balls-out start.
You should also spend a little time playing around with steering wheel position and seat angle/position. Some drivers like to sit close to the wheel with elbows bent, NASCAR-style, in order to "muscle" the car around. Other (like me) prefer arms more straight with the seat pushed back.
You'll also need to figure out braking points and turn-in points, especially if it's a faster course.
Back in the 70s, I used to run autocross events that involved starts on aircraft runways. Some of these events allowed you to get up to about 100 mph before the first turn. So in those high-speed autocrosses, a wicked-fast launch was important (and also impossible in the 42 HP Bugeye Sprite I was using
In shorter courses, I've seen people spin-out at the start because they were too focused on raw acceleration.
If you are able to record times and mount a video camera (your phone would be fine if it is in a sturdy mount), it can help in self-critique and improvement.
Eventually you will want to be able to maintain a pace where you are "almost never coasting" (almost always accelerating hard or braking hard).
But this is a learning process and no one is fast at first.