Great article. My experience with Kelly Criterion and Bankrolls comes from some stocks, MLB betting and poker. I have a few nuanced things to say:

1. For the hobbyist, losing your bankroll isn't usually a problem. If you're able to reboot your bankroll if you bust then go ahead and make Kelly-sized bets.
2. Kelly Criterion doesn't give great guidance on how to make several bets at once. There are some approaches to this: the easiest is to divide the size of your Kelly Bets by the total number of bets you want to make.
3. Although the Kelly Criterion is optimal, it's hard to implement in practice. Correctly estimating the terms is hard. There are often minimum and maximum restrictions on the size of the positions you can take. Also, early loses can really wipe out a bankroll. For these reasons, some people recommend dividing your Kelly Criterion by two or more. These are called half-Kelly or quarter-Kelly bets.
4. Kelly Criterion is primarily known amongst gamblers - but it has very wide application. Think of the Kelly Criterion as a way to optimise return on your information advantage in probabalistic situations. That first means you have to have an information advantage.