Calligraphy pens not laying ink evenly
Have you removed the protective (oil) coating of your nibs? Some people burn their nibs (over a candle, for example), but doing this they also re-temper the metal of the nib. (Don't do this if your nib is attached to plastic, of course.) I'd recommend to remove the coating with a Q-tip soaked in nail polish remover (acetone) (you can even try lemon/lime juice).

Some reviews of Manuscript calligraphy kits are pretty bad. If nothing works, maybe try a better nib (e.g. Brause dip nibs with Indian ink).