Best Laundry Soap For Baby?

Betthany • 22. Married my husband 6/28/14. Expecting our first little boy 1/8/15. Stay at home wife currently.
I recently started shopping for our little guy; which means onesies, pants, etc. However, I need to wash all of it before he makes his arrival into the world. Being a first time mom, I have no idea what laundry soap to use for his clothing and bedding. Any suggestions? Also, I would prefer if it was an affordable option but am willing to spend a little bit if it's good quality. So, favorite laundry detergent for baby?