When you’re exercising indoors, you can usually do without a jacket. If you like, you can start off with a light sweater jacket and take it off later once you’ve warmed up.
Otherwise, the same rules apply for indoor sports clothes: Make sure they are breathable. Nothing is more unattractive than a wet T-shirt that sticks to your body like a second skin.
Pants or Shorts?
Whether you opt for pants or shorts is just a matter of personal taste. What do you feel better in? If you sweat a lot, you’ll want to go for shorts or knee-length pants. If you’re only going to be doing gentle exercise and won’t get hot so quickly, then long pants will be fine too.