Ahh, the SPRINGTIME OF YOUTH!
Well if you're going to do the focus targetting thing, then yes you'll have to make new macros for every new spell that you want to target off of your focus. It's either that or have an assist button that you spam before every spell cast.
That sounds troublesome to me.
So how do we hack your life and make it a little faster?

1 possibility: Instead of making a new macro, just add on to existing macros by changing

/target focustarget
/cast Smite

to (for instance)

/target focustarget
/castsequence reset=7 Shadow Word: Pain, Holy Fire, Smite

The reason for the reset=7 is because 1 second global cooldown from SW:P + 2.5 second cast time for Smite and 3.5 cast time for Holy Fire. These numbers change depending on spec, etc, as do your powers (I didn't include stuff like Mind Flay or Vampiric Embrace)

Check http://www.wowwiki.com/Useful_macros/Priest for more... useful...macros...de la priest.
-McBooty L. Jackson