I would say protein powder. Creatine is a really good supplement to take but it's naturally occurring in food. The three foods that are the highest in creatine are beef, salmon and tuna.
One pound of beef will contain around 5g of creatine. One pound of salmon will contain roughly 4.5g of creatine. Each can of tuna will contain about 1.5g of creatine.
Theoretically, if you base your diet heavily around those foods and are able to get about 5-10g of creatine through food alone, you wouldn't need a creatinesupplement.
Most people would really struggle to get 6 whole food meals of protein in per day and a high quality protein shake is a very easy and cost effective way to help reach your daily protein requirement.
For a whey protein - you want to see nothing but that in the ingredients list. Whey protein, natural flavours, a natural calorie free sweetener like stevia and then maybe some salt, soy lechitin and cocoa powder. There are a lot of good products on the market. I personally use isolation from n2bm.com. A good whey isolate should be pretty much fat and carb free. Isolation has 26g protein, 1g carb, 0g fat per 30g scoop.