I think I'm the only person to go through round 1 of the academy in "auto".
I'm a GT noob. Got the game for Chrismas and didn't start playing until Jan.
It's strange, but I have always shifted with an old-fashioned stick and "H" pattern. (IRL) I actually have to "think" when I use the simple (should be easier) sequential stuff.
When I'm in student's cars at the track, I just leave the sequentials in "D". (Maybe use some version of a "sport" mode.)
In between round 1 and 2, I spent the week "learning" manual. The "stick" on the side of my wheel is a PITA, but the buttons on the back of the wheel are much easier. (Didn't realize the buttons until about a week ago)
The cars are faster in manual than auto. You can downshift a little early when braking into a corner and bacck off the brakes a bit sooner. (while still keeping the nose down and still getting the car to turn.)
Also, you can short shift on corner exit to reduce wheel spin.
You can also ride the limiter when needed. The Cape Ring replay I used in round one was riding the limiter in 4th around the circle while I had a heck of a time with my auto going back and fourth between 4th and 5th.
I still screw up now and then, but I'm glad I forced myself to use the manual mode.