Network Questions- Multiple systems and drives

Goal- To be able to connect multiple machines to a network and access multiple drives, printer, av, etc. Also I would like to add a network firewall for security.

Two MacBook Pro's- Internet, Two separate single drives (My working drive and Wife's working drive), Drobo 5N(This is purely an archive backup for my wife's photography business), network printer
iPad- Internet, Network Printer
Windows 7 Laptop- Internet and access work via VPN
Surface Pro- Internet, two separate single drives, Drobo 5N, Network Printer
Apple TV- Internet

We try to keep only items we need day to day on the computers, every thign else stays on the working drive or the Drobo 5N. I would like to add an additional Drobo 5N for all of our personal documents, pictures, etc.

We are currently using the ISP provided router/modem. We have a Time Capsule that is unopened and can be returned if needed.

What would you all recommend.

Thanks for the advice.

TankJKU