as Clive has suggested.. its wise to read the EI article as it outlines WHY we dose and how to dose. Irrespective of which route you take, its worth reading this first.
There are many schools of thought, alot will depend on your tank size, how much light youre using and your available spending limits! While TPN is good, its very expensive if youre trying to dose something like a 230litre! but very good for smaller tanks.
The best thing to do would be to try to get some background knowledge first, then you can make an informed decision.