Ideally, you would record in a sound-treated space, like the Digital Studio’s Podcasting Room, but when that is not an option, you need to be as strategic as possible about the space you choose and consider its level of reflection and ambient noise.
You also need to be mindful of the mic you are using and its placement. Here I have recordings done in my living room using five different mics. You will see that you can considerably improve the sound even when using basic headphones or spending $25 on a lavalier mic. There is also the option of buying a decent condenser or dynamic mic for around $80 and up.