How many feet of track you have; how many switches; how many loops of track; whether they are electrically connected or not, can all be factors in how many connections or "power drops" you need. You will get varying opinions, but I feel a drop every 6-8 sections of Fastrack should be sufficient.
You can then backtrack and see how many terminal blocks you need - for instance if you have 175 total track sections in your layout, then 175 track sections divided by 8, equals 21.875 (22) connections and you would need two (12 port) terminal blocks and have two unused terminals. You could also buy a 24 port terminal block and only need one with two unused terminals.
