The way I actually did it was 21 lessons per day (seven batches of three lessons each), but only for three days a week. I spent the other days of the week focused on grammar, reading, etc. instead of doing new lessons. I found it easier when I could have one main goal for each day.
This schedule usually kept my Apprentice items around 50, and maybe around 100 reviews per day at the worst of it. I typically leveled up every 15 days or so, so it’s not a super fast pace, but it worked well for me when balanced with other areas of study.
In case you’re curious, I wrote up a few more details when I hit level 60, over here.