I found the regular simple protein powders to be fine.

If you use a regular protein powder then make sure you're also taking 1 'heaping' teaspoon of creatine per day too.

I like the Optimum Nutrition Extreme Chocolate (https://www.amazon.com/Optimum-Nutrition-Standard-Extreme-Chocolate/dp/B000QSTBNS) but go with whichever you like the taste of best.

Make sure to get a shaker cup (like this: https://www.amazon.com/TOP-QUALITY-Shaker-Blender-14/dp/B01DTHWY5O ), it helps make sure it is good and mixed up.