Hi,

Running the lowest front gear and highest rear gear as a typical gear
is not good as you then don't have a close higher gear easily available.
(Well you do, but involves double shifting, up font, down rear.)

The front high gear and a medium back gear should be nearly
the same and may be more a flexible way of riding that gearing.

Not saying you cannot do it, but most of the time the highest
rear gear should only be used with the highest front gear,
and the lowest rear gear with the lowest front gear.
(For two front rings and a close ratio set on the back.)

Sounds like the front big ring is never used. Probably
because double shifting is not understood properly.

Going to more gears on the back either gives you
closer ratios or more range, for the latter you need
to make sure the derailleur can handle the lowest cog.

(Mine can't handle a bigger lowest cog than the one fitted.)

rgds, sreten.