You can earn Grade 2 and above by simply conducting what we call Patternwork utilizing the touch and go method to accumulate Landings and XP while getting a better trust with the aircraft you are flying. I would highly recommend aircraft such as the C172, C208 and SR22 for this. Start out with aircraft that fly at relatively slower speeds than an A321 or a B787.
Have a look at this tutorial and many of our other great tutorials for flight.
https://community.infiniteflight.com/t/remaining-in-the-pattern-tutorial/42567/1