What hardware do you currently have?
How much data are your devices using? Some could be low consumers of data even though connected to your network.
What is your Internet plan? The Telus My Wi-Fi app should show your top users of Wi-Fi which might help to determine what is using the most bandwidth.
It depends on what those devices are doing. I have between 40 - 50 devices connected (6 wired, rest wireless) at any given time and I have no issues. I'm on Internet 75.