Depending on what you are working on you are going to want a system (even a laptop) with multiple cores and a decent graphics card. Most at home training can be one in virtualization and having enough CPU cores lets you emulate more targets or components at once. A good Idea for this is to pick up a 1 liter business PC and start with proxmox on it. Cheap home server to get you started for about $100.
@P-One-X