• A set of dumbbells
• A 15lb aluminium Olympic lifting bar and two collars (Muscle Clamps are very good)
• Weight plates for your Olympic bar...2 x 2.5lbs, 2 x 5lbs,2 x 10lbs, 2 x 25lbs and 2 x 45lbs
• A squat rack or squat cage
• 3 Swiss Balls in 55cm, 65cm and 75cm sizes. The Classic Ball sold by Fitter International is very good. 

If you really want to be comprehensive then you could also add an adjustable single stack cable system, a few wobble boards of various sizes, a weight lifting bench, a back extension bench and some Kettlebells.
It's usually better to make sure you have plenty of floor space for stretching and exercises like lunges, Swiss Ball exercises etc
Most people cram far too many machines into a tiny area, completely eliminating any real "space" to exercise in. Many commercial gyms make the same mistake.
Remember...your training results have very little to do with how much equipment you have in your gym. What matters is that you train regularly, work hard and think carefully about what you should be doing in order to get the results you are seeking.
With appropriate thought and planning you can get great results with just a set of dumbbells. 

Most people assume that if they have pain it's because something is too tight and that if they could just figure out what that something was then they could stretch it and the pain would go away. This is an attractive idea because most of us have noticed a loss in flexibility as we got older. However, there is another possibility and in order to understand it we need to get to grips with the concepts of instability and hypermobility. Some people are naturally a lot more flexible than others. You can see this even in young kids. The very flexible ones tend to end up doing well in sports like gymnastics, dance and swimming. The really tight/inflexible kids tend to end up in sports like distance running, rugby or boxing. The genetic tendency to be very flexible is called hypermobility. The opposite of this situation is called hypomobility. When kids who are naturally hypermobile turn into adults and start to exercise less and lose muscle tone they often get pain because of instability.

A good example of this is the shoulder joint or gleno humeral joint. This is a ball and socket type joint that requires that several muscles be functioning optimally in order to keep the head of the humerus in the socket. An ex-competitive swimmer who swam 30,000m-50,000m per week as a teenager, but who is now 35 and hasn't been in a pool for over 10 years, will often get shoulder pain because the muscles that hold the joint stable are no longer in good shape. We have seen cases where you could quite literally pull down on somebody's arm and watch the humeral head move out of the joint, often accompanied by a sucking sound as the joint subluxes. In cases of such obvious instability, the joint must be re-stabilised using techniques designed to upregulate the function of the key muscle groups. Doing a lot of shoulder stretching invariable makes the instability (and the associated pain) worse.

The spine is another area of the body where excessive mobility often causes pain. We have seen many dedicated yoga enthusiasts, with incredible flexibility, who have chronic back pain which is made worse by the amount of aggressive stretching that they do every week. Doing less yoga and stabilising the spine with slow tempo or isometric exercises usually brings relief.

The bottom line is this...if you have pain that seems to be aggravated by stretching, try doing less stretching and find somebody who can help you identify whether instability is part of your problem.