You can do Pilates. It gives you a good enough workout & you feel relax as well. You can go on YouTube & search Pilates for pregnant women & see which one you might be comfortable doing
I just stick to walking... whether its outside or on a treadmill. You can go bike riding as well. Squats, lunges... simple stuff. Don't do anything where you are putting strain on your body or where you won't be able to catch your breath.
You can do pregnancy yoga, or just walking or riding a bike. Just make sure to not overdo it :)
My doctor tells me swimming is really good. Yoga and Pilates are my favorite though
Basic walking 30 mins a day is great, but you can do other things as well. The biggest thing is to not overheat your body because it's bad for the baby.