Building a bankroll from scratch is a bit of an awkward wording, since you need to risk money to win money in poker. Here are factors that affect your bankroll's growth
- Skill level and understanding of the game
- Bankroll size relative to your buy in
- Variance of the game
- Level of competition
- Rake and rakeback
Maximizing skill level and bankroll growth while also minimizing variance, rake, and skill set of your competitors (basically the inverse of your skill set) are necessary to grow your bankroll.
Without getting into any complex math in this thread, I will say that its a great idea to avoid stakes below $100NL, if possible, simply because the rake is otherwise such a large portion of your potential winnings, reaching upwards of 2.5BB/100 when a great win rate for a skilled player is 4.0bb/100.
Of course, that means that you also need a very solid skill set because just learning the rules and hopping into $100NL games with a $500 bankroll is going to get you owned. Read a lot, maybe find a good poker training site when you can afford it, and post and interact in forums a lot. Gradually, your skills increase. Learn to look at situations in poker objectively. The list could go on forever.
Variance is important because it affects the amount you need to originally invest in the game. Speaking from personal experience, it can be much easier and less time consuming to earn money in another way and then to risk it with poker. What you want to do is find the point at which your hourly rate taking a low- or no-risk job (even if it's an odd job!) matches your poker hourly rate and accounts for the variance and rake you have to face. For example, if you can make $15 a hour working somewhere, then why not do that and save money versus playing $0.01/$0.02 with an hourly rate of $0.50? If you can have 30x the hourly rate, then why not get it elsewhere and then hop on the poker variance train when it makes sense for you: when you're studied enough and when your bankroll is large enough.
Game selection is a big factor. If you can find a game wherein your average win rate is 2bb/100 versus another game wherein you break-even, then seek out ONLY those games you can beat. Once weaker players leave, don't be a dork and break the game immediately; but, play a few orbits and if the weaker player doesn't reload or return, then try to find a solid table to replace the one you can no longer beat for an acceptable amount. This requires discipline, so get used to being honest with yourself and your skill set.
The site on which you play is a large factor, particularly at lower stakes where rake is a large portion of bankroll, and conversely, rake back is a large portion of winnings. Make sure you get a solid rake back deal, but also know that incredible rake back deals are often paired with unproven or unsafe poker clients. Do your research at this point because when you're just starting off, it's likely you're going to be playing on one
poker site. Think of it like a HUGE poker decision at the poker table with no variance - it affects your bankroll a lot.
In the same vein, be sure to take advantage of deposit bonuses. I ran up a lot of my starting bankroll hopping from site to site with a smaller win rate. While I got practice, I also unlocked bonuses that effectively added 10-50% to my bankroll. Make sure you can step up from bonus to bonus as well. So for example, one safe site may offer 100% bonus up to $200 bonus (meaning you deposit $200 and they'll give you $200 with some stipulation like you need to play a few thousand
hands before cashing out) and another site may offer a bonus like 50% bonus, up to $1000, meaning that they'll give you $500 if you deposit $1000 and for a different stipulation (the number of hands played will likely be different). Make
absolutely sure that you can maximize your value and get the most out of every bonus. Make sure you have $200 for the $200 bonus and make sure you have $1000 for the $1000 bonus. Effectively, this is going to add several BB/100 to your win rate, and at this stage, you'd be lighting a significant amount of money on fire not to take this seriously.
I hope all that helps you out! Good luck getting started. Once you reach a point that you've over 50 buy ins for the limit that you can beat for about 2bb/100, it's pretty easy to stay put and then just work on your game until you can move up another few limits, but over more time, since it's much more difficult to get good enough to move up once you get higher than it is to get enough money to move up stakes when you're lower.
There are marginal returns on both sides of the coin: playing to win the most and making the most money you can to play the highest you can play. Just make sure you have your sites aimed at the best outcome for you and grind your face off if you really want it!