The free version of Blynk (which is the one you are using, where you buy energy) is limited to 5 devices.
You could set-up your own local server to get around this, but in my opinion there is a better way.
One of the things that gets a bit messy with Blynk is when you are trying to pull-in data from multiple devices and process it on another device (things like taking temperature readings via a dedicated device then using that data to control a heating or cooling system with another device).
This gets messy in Blynk because of the need to use Bridge code, which isn’t very intuitive and can be difficult to get working first time around.
My preference for smart home projects is to go use MQTT messages to obtain data from devices, and to send commands back to devices.
Node-Red can then be used to act as the gateway between your devices and Blynk (either using the cloud server or a local server). In this setup you only really need one device within Blynk, although I find it easier to use two or three devices and this has the advantage of giving more virtual pins to use.
This approach also allows you to use Tasmota to re-flash off the shelf devices like Sonoff switches (and often this can be done without the need to open the devices).
Here’s a topic which explains my approach…
Pete.