We keep it fairly cool in our room because I'm scared of overheating - always have a fan on and the house is never warmer than 74 degrees at night. We dress LO in a short sleeved onesie with a miracle blanket or halo sleep sack swaddle but I hear people adding a fleece sleeper to the mix. That seems like a lot to me but are we underdressing LO? He seems comfortable and never feels cold.
If its cold out I'll put him in a cotton sleep and play plus the swaddle, but we set our heat to 70 so it's never freezing. We live in Florida, fwiw.