Here is a quick list of protein powders I send out to my clients when they're looking for a first protein powder purchase.
Two are milk-based, two are plant-based.
Optimum Nutrition 100% Whey Protein
True Nutrition New Zealand Grass-Fed Whey (unflavored, nothing added)
Plant Fusion Complete
Sun Warrior Warrior Blend
This isn't a complete list, and there are pros and cons for all four. But it's a good starting point, they all taste good (or not at all, for the New Zealand whey), and they're fairly easy to get.