As B26 says, an unarmed transport is quickest and easiest. Armed? A heavy cruiser or a battlecruiser.
I agree. if you want to just run it around, put-putting, some transport is for you. now, if you want to blow holes in everyone else, a small battlecruiser or battleship is the ticket.
I'd have to go for a polystyrene towed target ship. Helps hone those gunnery skills, and it won't shoot back.