What would you recommend?

ok i plan to get one of those new macbooks and i already have a pc. im looking for an external storage system so i can transfer the files i have on my pc to my mac so they can be in-sync. i was looking at the time capsule that apple has but its a little confusing for me. plus, its way overpriced. im trying to look for something that is compatible with both a mac and pc with a minimum of 500gb of storage. ty