The time savings from a disk are HUGE. If I've got time I'll pull up the study that breaks down various savings over a 40k tt (aero helmet, no gloves, shoe covers, disks, skinsuit, aero bike, bottle on seat tube, etc). If I recall, wearing an aero helmet actually gives you the biggest bang for your buck.

Folks always assume that they'll blow around with a disk. That's not necessarily true. The wind is channelled around the bike and with a little practice you'll feel very stable.

If I were giving advice to a newish racer about time trialling, I'd say the most important thing you could do is learn to pace correctly. Read everything you can about TTs and then practice them (most racers don't practice TTing because they don't have a good course). These two things will help you be more effective than the "free time" saved from aero elements.