As a recreational player, you don't need any bankroll management - just do anything that maximises your fun; only play with your spare money that you don't mind losing, not with the money you need to meet your life expenses.
If you were to play poker professionally, I'd advise to stick to a rule of thumb: play at the buy-in levels where you have reasonable evidence that you're a longterm winner; if you have no evidence, start with the lowest stakes ($0.11-0.55) until you make sure that your skill is good enough to be a winner at $0.88+ (getting such a proof requires thousands of tourneys or a review of your play by a qualified coach). Don't take shots at the next level at all, no matter how much money you have, until you're totally sure that your ROI at the current level in the very long term is bigger than 10%.
But if you become a strong pro and suddenly have to make a larger than normal cash out for real-life reasons, you'll only need a small bankroll (my educated guess is that, for a pro, it's OK to move up once one has 50 BIs for the next level) to get back to your usual stakes, because the microstakes are much softer than your usual stakes at that time and you'll be already strong enough to crush the micros with much higher ROIs than your usual stakes at the time.
Optimal bankroll management for a pro is like trampoline jumping: you should be ready to move down at any time, maybe 2-3 levels down within a week in a bad scenario, but with bigger ROIs at the lower stakes, you'll likely bounce back soon enough, especially if you make a final table. And when the wind of variance blows upwards at the highest level where you're yet qualified enough to play, that's when you'll finally make money, but don't rush to play at a higher level then - first get the proof that you're a longterm winner at all the previous levels.
Most pros don't like to move down as often as I find optimal, because they feel like moving down is like being demoted (which it isn't) and that would put them on tilt, hence they find it more comfortable to play at levels for which they have 100+ BIs.
Bottom line: the skill matters much more in modern online poker than the bankroll size. A strong player doesn't need much; to a losing player, no money in the world would be enough.
