Easy to care for. The stores are full of adorable baby clothing and it is easy to get carried away with frilly dresses and sweater vests, and you will undoubtedly receive many of these outfits as gifts. But the most practical baby clothing is soft cotton or light wool, easy to wash, and easy to get on and off of a wiggly, wet or poopy baby. Layers work well as babies do not regulate their temperatures well.
See below. I would recommend 100% cotton, wool - appropriate for a season (don't keep baby to hot or too cold), easy washable, and easy to change: put on/take off, bright and colorful.
See below. Onesies are the easiest. Clothes you can get to diaper quickly. Lots of them as they will get messy quickly. Ziplock bags are great for extra supplies.