You may receive your first donation on the first day or after a few months. To earn money on Twitch, you need to know what encourages people to donate.
Conversation with a streamer
Most of the streamers communicate with the chat but can't react to every message. This type of donation gives the viewer the opportunity to ask a question or make a statement.
Try to react to them accordingly. Understanding when it's best to laugh it off or engage in a conversation is a valuable skill. Right answer could motivate your followers to continue dialogue via donations.
It is simple. You've made someone's day a little brighter. Maybe even not today, but they want to thank you for that. Some become your paid subscribers. Others donate from time to time. Such contributions are one of the most pleasant ones a streamer could get. Build the community, be nice to people and this will be your reward.
You can make your broadcast more interactive. Use polls to choose the next game, set goals that will reward the community for contribution. Give the people the opportunity to be the decision makers. If you know your audience well, it could be great fun for them.
Opportunity to stand out
The chat is moving so fast no one will know your little secret. More viewers lead to overflowed chat. That lead to a hive mind when the only way to talk to other viewers is via donations. Some people may try to troll you. Or make a joke.
Such donations are a part of streaming culture. People like to stand out and get some attention. It is entirely up to you how to react to this type of donation. Aggression can upset viewers, but some streamers made a name on raging. Know your audience to make the right answer.