Hi yung - good questiom, I'm nearly getting my first R7 toon (Darth Revan) and I only unlocked him in April - so I can say it will take about 3 solid months to go from G1 to G13 and then R7. Yes there was some help with the double drops, loads of crystals from GC and I treated myself to the hyperdrive bundle.
What I can honestly say though is once you get through the G13 barrier going from R1 to R4 is easy, R5 and R6 you have to use some purple salvage gear and R7 is lots of cantina energy for the cards etc - use cantina energy on the salvage and go for MkIII Holo scanner (?) for all the other salvage parts. If you've been playing for a long time and if you buy all the salvage in the shipments - you will have no trouble getting the easier salvage.