What should I keep in mind when buying a make-up base for myself?

Basically your skin type. Oily skin has base which makes the skin look Matt. Dry skin needs a little moisture so a cream base or a moisturising base does the trick. Normal or combination skin has its type as well. With regard to the colour you can choose a colour that matches your skin. Sometimes you will need to mix two shades to get the right shade. Check the shade on your chin not on your hand. Last but not the least. Duration. How long do you want it to last?? Creams last longer and are water proof , water bases are lighter. But don't last as long. You can decide accordingly. All the best.