Performing network design on such a network is not something that is trivial, nor can it be answered in a single post. I think the most important thing here is to keep the following principles in mind:
Separate your subnets/VLANs based on user requirements and security. Separate your server traffic from your Wi-Fi users and use appropriate access lists or other security features to keep those networks separate.
Make sure you have routing available between all subnets, most likely using inter VLAN routing on your Cisco SG300.
Make sure you have the required redundancy for connections to the internet, and for connections to your servers.
I suggest you take a look at these lessons which include more necessary principles for network design:
I hope this has been helpful! Stay safe and healthy!