My suggestion for knee pain and problems, is to buy clipless pedals that allow motion - and do not severely restrict your movement. I believe this is referred to as "float" in a pedal. The clipless pedals will allow you to pedal in a true circle - lifting on one side while pushing on the other - all the way through the pedal stroke. The float in the pedals will allow your knees to naturally position themselves in a comfortable position. As you are getting in shape, stay in easy gears (big rings in the back) and little rings in the front and increase your cadence as your strength and stamina build. I would work on cadence before speed and bigger gears. You can also buy a stationary trainer to place your bike on - to spin at home on days that you cannot get out on the road. Even 20 minutes a day will help. I think this is better than going to spin class - you don't have to find a comfortable position on every new machine you find yourself on. Talk with several bike shops about pedals - ultimately - you need to buy what feels comfortable to you - everyone has a style choice and pedal choice depending on the level of cycling they are doing.