If you want to become one of the best tennis players in the world, then you need to dedicate all your time to that, and you will also need some talent. And its a bit the same with poker. If "good" means able to compete with the very best, then you need to go professional and dedicate all your working hours to poker.
But if "good" just means better than average, or good enough to beat online micro and low stakes games, then its more important, how you use the time, you dedicate to poker, than how much time it is. It probably needs to be more than a few hours per week, but I really cant say, if 5, 10, 20 or 30 is the right number of hours per week for you to spend on poker.
There are plenty of people, who have spend a lot of time on poker, but they are still not very good at it, or they keep making bad decisions, that prevent them from having real success in the game. Like for instance:
1) Continuing to focus on bad beats / short term results instead of focusing on their own decisions
2) Refusing to make even a small deposit keeping themselfes trapped in
freerolls for way to long
3) Withdrawing even small winnings, so they keep themselfes trapped in microstakes games for way to long
4) Failing to implement bankroll management, so they go through repeated boom-bust cycles
5) Poor game selection like playing Spin n Gos or other close to unbeatable formats
I am a bit "guilty" of point nr. 3) myself, because well.... life happened, and my family got priority over poker. But all the above are thing, you need to avoid as much as possible to succeed in poker.
