PfcAJ
Contributor
I've just started diving dry as well. I try to use my BC for buoyancy as much as possible as I hate the shifting air feeling of the suit, but when it gets really cold I let air out of my BC and put air in my suit. Instant warmth. However, prior to an ascent I like to let air out of the suit and put air in my BC. Probably not the best policy when it comes to maximizing air use.
In time, you'll learn to run enough gas in the drysuit to fully loft the undergarments you're wearing. That 'instant warmth' you're feeling is the undergarment being fully lofted. A lot of people dive with a constant squeeze on their suit, only to reduce the insulative value of said suit. You'll find the sweet spot where the UG is lofted, but there isn't excess gas in the suit. Try it out, see how it works for you.