I workout at home and have the following equipment in my gym (the first 4 are IMO essentials and should be the minimum purchase for a home gym set-up - they give you the ability to any barbell exercise):


Power Rack
Standard Olympic Barbell with 2.5kg collars and 160kg worth of weight plates
Adjustable Bench
Weight Plate Tree (very helpful for storage of weight plates)
Powerlifting Bands Set (these are great for providing added resistance to the top of lifts, weighting push-ups, warm-up exercises, stretching and many more uses)
Adjustable Dumbbells 
3kg and 5kg Medicine Ball
Ab Wheel
Home Gym (Cable Station)
HeavyGrip Hand Grips
Concept 2 Indoor Rowing Machine
Boxing and Dip Station Stand
Foam Roller (excellent for getting rid of muscle tightness, improving mobility/flexibility and preparing/warming-up for training)

Dip Belt (great for weighting chin-ups too)
Weightlifting Belt
Tricep Rope
Plyometric Box (for box squats, step ups and various plyometric exercise such as on-box jumps)
Lynx Grips (for those that want a non-messy alternative to chalk, hate calluses or a make-shit fat bar - get 2 pairs of grips if that's what you want)
Harbinger Wrist Wraps
Interlocking gym flooring