Sometimes the best time is as soon as you can, weather permitting. I have been wanting to get gravel on the drive of our rent house but weather has not been cooperating. Finally, pushed to a condition of extremis (pulled the renter out with my tractor, twice) I just ordered large gravel, full 18 wheeler load, and put half on the drive, mostly in the deep soft ruts and some spread.
Using the tractor to fill the ruts and smoothing the drive to a great cosmetic appearance prior to adding gravel is NOT recommended. It isn't just a waste of time and it is actually counter productive. Fill the ruts with large gravel. This firms up the remaining material beside the rut giving it no easy place to squish to. Next, put rock where ever it is the softest. I underestimated the amount of gravel I would need but don't want to have to haul the other half from my house over a quarter of a mile to get it to that driveway. What I am doing is NOT optimal but conditions may not be optimal for months and I need results now so plan B is the best I can do.
I will be getting another full load (I forget if they are 24 ton or 24,000 lbs) today, Saturday, and that will finish the job with some to hold back in reserve to "fix" soft spots.
I wanted 4-6 inch but none was available so settled for 3-3 1/2 crusher run with fines. Later after the drive dries out and firms up (whenever that is) I will put on a layer of smaller diameter crusher run with the fines included. It has always been my experience that if you have decent drainage by sloping or crowning the drive and avoid letting torrents of water run across it that will "cut" a channel in it a good gravel job will last for years.
My drive way is going to get a little make over, a little fresh gravel for the most of it and shale near the house (makes a terrific looking and long lasting surface that looks sort of like blacktop only smoother. It has held up for years with little to no maintenance but it is time to freshen it up before our super wet conditions cause deterioration. Our average rainfall is about 36-37 inches. I got 55 last year and winter storms are bringing plenty so far this year. For my first time ever I have to be careful putting out round bales for the herd to avoid getting the tractor stuck.
Bottom line is... It may not be prudent to wait for optimal conditions if the deterioration you suffer while waiting could be expeditiously and economically avoided.
Pat