Way way back the first week of RAs, I made a post wondering if I was the only RA with rN water cannon. In that thread, I listed my skills:
r6 synth,
r2 Alchy Mastery, (1190 crystals to go. :-( )
r1 metal conversion,
r6 life drain (because life drain crystals sell well, and I can afk fish-- still r6 because AM is pain)
rC summon golem (to train early AM crystal making)
rE fragmentation (because I ranked it to F before I noticed that the success rate for cheap silk goes down)
Total level 11xx
edit: oh and I guess I have Mana Crystalization at r7 now too. (though I'm not sure what it was when I was accepted)
Everything not listed was rN.
The second week RA was out, I lost the title.
Because being an RA added bonuses to Synth, I was committed to getting my title back.
I ranked AM to r1. Nothing.
I ranked MaCr to r1. Nothing.
I ranked LD to r1. Nothing.
I ranked all my non-shock rN Alchy skills to rF (obviously a few were higher to meet prerequisites). RA again.
Since that time, I have live by the code, "Cover everything with at least rF, then specialize in the skills I want."
With the exception of 1 week when I failed to get 60 RA points, I have been an RA since.
Since re-acquiring my title, I have ranked water cannon to r1, chain cylinder to r1, fragmentation to rC (it's a cheap silk thing), and transmutation to r5. (because of an AP splurge when I woke up one morning and said, "I think, today I will become a mage." my other mastery skills are still rN until after I train Transmutation)
That's my story. Maybe it will help you decide what to do.
My suggestion, "Cover everything with at least rF, then specialize in the skills you want."