I cannot stress enough how important it is to have professional advice from a physical therapist familiar with MS when you get a wheelchair. The right fit, angles, wheels, cushions, materials, etc. can make all the difference.
Using a chair does not mean you need to become deconditioned. It means you are choosing if you want to use up your energy struggling to move spastic legs around a shopping mall, a sports center, etc., and then collapse at home or if you want to zip around in a well-fitted personal mobility device for errands and then have some energy left for family and social activities. It means that you might not cringe when someone suggests an outing.
But you have to commit to being active, just like any other priority.
Incidentally, many of those funky wheelchairs are designed for people who have spinal cord injuries. People with MS have different needs. A critical difference is arm strength and fatiguing easily.
Check out wheelchairjunkie.com for explanations of the components in manual chairs.
another one http://www.wheelchairnet.org/wcn_prodse ... ectwc.html
You can rent a chair while you wait for an appointment with the nice center. Do you have a Center for Independent Living near you? You might be able to go and check out a chair temporarily. Or maybe your local MS Society has a lending closet.
Consider this when you wonder about how much money to invest: the design will have an effect on the user's entire body. It can wear out shoulder joints if it's not easy to propel. It can cause pain and increase spasticity if the fit and angle are not right. It can heighten risk for skin breakdown if the seating is poor. But the right chair will increase independence and comfort. I would invest in a decent chair and a knowledgeable therapist to help evaluate the right fit.