An experienced winning player could opt to chose an aggressive bankroll management style. An advantage of this is you can wager a higher percentage of your bankroll and thus hopefully winning fast and moving up to higher stakes quickly. The disadvantage is you can lose a lot quickly too and you'd have to move down again or deposit more money into your account. But this is usually a bad sign, because winning players should try to deposit only once and manage their BR properly.
A safer route is to wager a very low percentage of your bankroll. A very important thing, especially for new players, is just to have fun. Try to have fun even if you only make $0.50 an hour. It is much better than playing higher, against tougher opponents, getting frustrated about the huge swings and perhaps even losing long term. Gamble responsibly and it will probably never keep you up at night after a huge losing session. Playing lower also avoids tilt more.
I am just going to give some rough numbers here for both cash games and tournaments, as it was not clear for me if you meant both or the one or the other.
So for an aggressive style you need around 20-40 buy-ins for cash games and 50-100 for tournaments. For a safer style you need 100-200 buy-ins for cash games and 100-1000 buy-ins for tournaments. I would recommend the safer style. For 100-200 buy-ins cash you need to deposit $200-$1000 depending on the lowest stakes that are available. For some this might be a lot, but if you watch some videos, join a training group, buy some training/tracking software, basically invest some money into getting better, the fast majority should be fine beating the lowest stakes. It can hardly be the worst decision you make in your life, but it can turn out to be a great one. For tournaments you probably need to deposit around $500. Then mostly try to play the tournaments where you have 500-1000 buy-ins and then maybe on saturday or sunday or whenever you feel really good you can play one or two tournaments where you only have 100-300 buy-ins complemented by some lower, usual buy-ins.
Usually live you play for a lot more money. Try not to do the same online, it is a totally different environment. When playing online don't think about winning money, but think about winning big blinds or buy-ins. Good luck.