If there was to be no other choice of supplements in the world I would opt for Spirulina! Its high in: Vit B1 thiamin, B2 riboflavin, B3 niacin, Copper, Iron, Protein plus: decent amounts of magnesium, potassium and manganese and small amounts of almost every other nutrient that your body need.
Goes Well With:
many things!

A great way to top up protein via a superfood. I mix it into my pre-workout and protein shakes. It’s very powdery, leaving quite a mess on your fingers and worktop. Turned my poo green. Has a very slight algae smell and taste but if you drink it quick it’s unnoticeable, but wash your shakers out immediately to minimise the fishy smell over time.
Goes Well With:
Water Preworkout  Protein shake

This thing looks so nice, smells so nice and tastes so nice. And it's good for your health also! Makes food very green (beware!), which is cool! Has a slightly sweet taste - but only a bit. However, since it's so powdery, maybe it's better to sell it in tubes/pots/cans/jars? It's quite hard to get this powder out of bag with a scoop without making your hand look like it belongs to Hulk.
Goes Well With:
Food

This is the greenest green I ever had:) I am impressed by the intensity of the colour and the soft consistency of the powder, as it is easily mixable with yoghurt and milk. I didn't like the smell and the taste so much, it has a bit of algae smell, which is actually good and shows the authenticity of the product, but I don't get used to it. That's why I blended it with an orange, yoghurt, ginger and a little bit of water. This is my Spirulina Smoothie since few days and this way I really like it. I use it since 5 days and I can tell, I feel good, vitalized and healthy. I had a little cold, my nose was running and after two days everything was gone. It is really worth to buy it, I only can recommend.