Has anyone else done giveaways on gleam.io before and how much growth has it done for your channel if you have. Thanks in advance
I have done quite a few with varying results. If you are just one channel doing a gleam giveaway you probably aren't going to get amazing results but there are other methods which can be done that can yield great results.
Get a group of content creators in your genre and everyone can make videos on their respective channels with a link to the giveaway with the prize that you are giving away. The other people in your genre will gain subscribers without having to do anything but upload a video talking about the giveway. As each YouTuber adds their videos you can update the gleam giveaway as needed with their channels added. Have the main entries be "Subscribe to so and so" with each content creator listed. You can have unlocked entries as well such as follow on Twitter, like on Facebook and so on if you want to but make sure that the "subscribe" is a prerequisite first. With having multiple content creators in your genre uploading videos on their channel, you will have a lot of eyes on your content that might like what they see.
The best overall option is get a group of content creators in your genre and have everyone chip in a prize. The more prizes the more incentives for people to join the giveaway. It is trickier doing this way than the other due to having multiple winners and trusting the other YouTubers come through on their end with prizes but you can easily get hundreds of subscribers.