To level up as quickly as possible, all you need to do is consistently get the apprentice reviews for kanji and radicals of the current level right. It’s not that hard if you put your mind to it and put extra effort into them. You don’t have to remember them long term, just for 3.5 days, and then you can repeat with the next level.
To further demonstrate, here are my accuracy stats for the last month. As you see, it is possible to level even with really terrible accuracy stats, as long as you do well on the reviews that matter. Notice how I have high accuracy on the apprentice level radical and kanji reviews and terrible accuracy on everything else.
radical:
Overall: 91.9% (124/135)
Apprentice 1: 100.0% (7/7)
Apprentice 2: 100.0% (7/7)
Apprentice 3: 100.0% (9/9)
Apprentice 4: 100.0% (11/11)
Guru 1: 89.5% (17/19)
Guru 2: 91.3% (21/23)
Master: 88.5% (23/26)
Enlightened: 87.9% (29/33)
kanji:
Overall: 89.5% (2481/2772)
Apprentice 1: 99.0% (303/306)
Apprentice 2: 99.4% (313/315)
Apprentice 3: 96.2% (357/371)
Apprentice 4: 95.9% (462/482)
Guru 1: 88.6% (441/498)
Guru 2: 76.7% (323/421)
Master: 80.7% (205/254)
Enlightened: 61.6% (77/125)
vocabulary:
Overall: 77.2% (8830/11432)
Apprentice 1: 74.8% (1002/1340)
Apprentice 2: 87.0% (1171/1346)
Apprentice 3: 84.8% (1702/2006)
Apprentice 4: 83.8% (1748/2087)
Guru 1: 71.4% (1362/1908)
Guru 2: 69.9% (995/1424)
Master: 67.3% (565/839)
Enlightened: 59.1% (285/482)
Overall accuracy: 79.748% (11435/14339)



