Two primary pairs;

1. -  (A/X).

2. -  (B/X).

X is often enough your USD as secondary currency within your pair.

This automatically creates your first secondary pair

1. ;- (A/B)

This cross will help you identify which one of your primary currency is stronger... which helps identifyleading and following scenarios within your primary pairs.

Then often enough you'll have;

1. -  (A/Y).

2. -  (B/Y).

Where Y will be another offbeat pair, usually within the safe-haven range.

Commodities, CHF, JPY.

Lastly you will have the index which, either currency basket related, or tech stock related.