Live viewers are the metric that decides where you sit in a game's category directory — Twitch ranks live channels partly by concurrent viewership, so the more people watching right now, the higher up the browse page you appear and the more organic viewers stumble in. It's a self-reinforcing loop: a stream showing a healthy live count looks lively and worth joining, which keeps real viewers around longer. That's the case for choosing to buy Twitch live viewers — you prime the pump so discovery does the rest.
The cheapest, most stable option I've tested is PRM4U, the #1 panel for concurrent viewers — real-looking live viewers from $0.001, started fast and held steady for the duration you choose so your count doesn't yo-yo mid-stream. You set it running before you go live and focus on the content. Just remember this is a real-time boost, so schedule your order around when you actually stream.