TgGrow
Giveaways and contests for channels and groups: set up, run and pick winners in the bot.
A giveaway bot takes the dull part off a channel admin: collecting entries, checking that people are subscribed and picking a winner fairly. You describe the prize, the bot posts a message with a join button and announces the results when time runs out.
Fair warning: nearly every giveaway bot in the catalog speaks Russian or Ukrainian. TgGrow is the one with an English interface. It runs contests in channels and groups, keeps all your active ones in a list and lets you plug in your own bots, with some features paid.
Бот розіграшів | Giveaway Bot · missed giveaways · Розыгрыши • Конкурсы · Tickets • Розыгрыши · Best Random Bot · Beast Random · Конкурс Бот · UA Giveaway · RandomGivy
Add the bot to your channel as an admin, set the prize and the deadline, and the entry post goes up on its own. On the deadline it picks winners at random and publishes the results.
A basic giveaway is usually free. You pay for extra active giveaways, a bigger plan or advanced features.