Three refreshes of 120 energy is 360, you get 120 every 24 hours too plus the bonus 45 energy to give 525 cantina energy a day. Use the 8 energy nodes and you can sim 65 battles a day, provided RNG is neutral and you get the 1/3 drop rate you can expect get around 22 shards a day.
This will cost 300 a day but you should only need one day of Ben farming and 4 days of Luke farming costing you 1500 crystals in refreshes. Luke has his light side node too and might appear in guild events store so keep an eye out.
Provided you just focus in those two you should get them to 7* with at least one day left. Still need to gear, level and mod them for the event though.