On longer training rides, you may want 2 bottles - most bikes will take 2. Bottles can usually be obtained inexpensively. Padded capris are good - shebeest makes some really nice ones.

A bike computer is useful to have - particularly on organized rides. It will help you follow the route - most tell you to turn ever x.x miles. However, on an MS ride, the route is usually really well marked, so it may not be necessary. I'd try to wear a wicking shirt - doesn't have to be a jersey. Just something to keep you comfortable (something you wear to the gym or walking should be OK for now).

You will also need a way to change a flat on your bike should you have one far from home. There are lots of flat clinics - and you tube videos - just make sure you at least have the equipment (pump or cartridges, spare tube, tire irons). You are pumping your tires up before every ride, right

CA