Probably the best advice is to not do all lessons at once. The actual amount of lessons and the times you do it at will vary from person to person, as everyone has their own pace.
For me, the amount of lessons I do will depend mostly on the number of apprentice items I currently have, and the number of lessons I’ve already done that day. I try to keep my apprentice count below 150 (preferably even 100 if possible). Apprentice items are the items that come up in your reviews most often, so the more you have the more reviews you will have on any given day. Keeping the amount low enough ensures that you aren’t faced with days where you have 300 reviews to do (which I had for some levels when I still did all my lessons in one go, which I regretted afterwards).
I will also try to limit myself to not doing more than 20 to 25 lessons a day. Since the SRS works with regular intervals, if you do 50 lessons at a given time, you will have 50 reviews to do 4 hours later, and large sessions tend to burn me out. I prefer to spread the workload out over the week to prevent this.
Now there are some exceptions to this, for example, since radicals don’t have readings they tend to be a bit easier to remember correctly (at least for me), and some related vocabulary can be treated as a single item (for example if you know the numbers the vocabulary for the different months tends not to be too hard to remember, as January is 一月, February is 二月, etc.), so I’ll treat all of those as one item.
The most important part is just getting into the routine of doing your reviews and making steady progress. Your final goal is to learn all the kanji, so finding a pace and schedule that works for you is the most important part. And if you run into any difficulties, just come to the forums, people here are more than willing to help.
Also, I can definitely recommend checking out the ultimate guide @tls mentioned, it really does a good job of explaining how to manage workloads on WaniKani and what pitfalls to watch out for.