How to manage your bankroll
Proper bankroll management is always about looking to make sure that you are playing the ideal stake level at every point in time. What we are looking to address and manage here is your so called risk of ruin, which is the risk that you'll lose your entire present bankroll.
Now ruin may not be the appropriate word here, as the consequences of busting out can differ depending on your situation. For instance, a new player who makes a small deposit and can easily deposit a similar amount if needed, with the expectation that it almost certainly will be needed, is going to face almost certain odds of this so called risk of ruin.
He or she does not have the skills to be profitable in the first place, so it really doesn't matter what stake is chosen. The end, the ruin, is pretty much inevitable. On the other hand, if you play online poker for a living and losing your bankroll would be disastrous, then that's a different story.
Bankroll for regular players
Perhaps your real world skills aren't very significant, and if you bust out, you may be faced with years of working at a low paying job while trying to rebuild your bankroll, and also face the indignity of a severe downgrade in income along the way. So this is definitely something that you are going to need to protect against.
So as you can see proper bankroll management is not just a matter of needing a certain amount of big bets or buy ins to protect yourself against this. We first need to look at the level of protection that you will need, and this will differ according to what you need to protect.
Once again, if you are not profitable yet, your risk of ruin is very high, and what you want to focus on here is making the cost of your poker education comfortable. If you only have modest means, you then may want to consider looking to beat the smallest stakes before you consider moving up to higher ones.
If you have more significant resources and want to accelerate your development, you may then want to consider playing a bit higher up on the ladder, where the competition may be better and thus provide you with more opportunities for growth.
Once you do get profitable, you do need to protect the revenue stream that you are generating. While newer players tend to get too aggressive in their bankroll management, due to their lack of understanding, a lot of seasoned players actually develop habits that often go too far the other way, erring on the side of caution.
Proper bankroll management
For instance, some players may end up playing 16, 24, or more tables at their current stake, and have plenty of money to take a shot at the next stake up, but they are intimidated by it. Now, it might be true that they presently may not be good enough to play that many tables at the higher stake, but that doesn't mean that they should not venture out into it anyway.
Poker players tend to think of bankroll management as an all or nothing thing, black or white so to speak. It's like they are married to their current stake and if they want to move up they need to get a divorce and then re-marry. In reality, moving up stakes should be seen more as first fooling around on the side a little, and if the relationship develops, then you can consider pursuing things more seriously.
It may turn out that you may not be able to play as many tables at the higher stake as you do at the lower one, however, your earn rate per hour may be higher with less. In fact, it is recommended going back to a single table at a higher stake, and then add more as appropriate. This way you minimize the added risk by being able to get a good feel for things at the higher stake.
As far as what amount of big bets or buy ins that you need at the higher stake to commit to it, since we're not really committing to it right off the bat in the first place, you can feel free to take a shot at it by dedicating only a modest portion of your bankroll to it. Then, if things work out as planned, you can dedicate more, although it's always best to have an exit strategy if needed, meaning moving back down if need be.
So to sum up, if you are a losing player, it's generally best to play the lowest stakes until you can turn things around, to minimize your losses until you get profitable. If you are profitable, you want to be playing in the most profitable stakes while still managing risk, which means that you shouldn't be afraid to take shots at higher stakes, but at the same time you shouldn't be willing to lose too much while doing so. This way you will always be in the best position to maximize your results and keep your risk at an acceptable level.