Maybe a good place to start is draw out your vision of the space. Where you could see what machine and how much power that appliance will need. Include tools you will or plan on adding and research how much power they will draw. Don't forget lights, switches, fans, heaters. It's easy now. Difficult to add later. Then talk to a qualified electrician. Maybe you can do it all yourself. Maybe the sub panel box can be wired into the garage and you can take it from there. Like anything else there is a learning curve and only you can determine skill level, and comfort level. The electrician may even work with you by letting you do the dirty work of running the wires and mounting the boxes. Then they come in and do the final hook up.