I have 78/100 Old Ben and 18/100 Luke. I have 1600 crystals and 6 days. I don't pay to play. Is it likely with refreshes to get both to 7 stars in time or should I spend the crystals elsewhere and ...
You will have absolutely no problem getting him. Both Ben and luke are low cost cantina characters. 3 refreshes of 100 a day will probably yield about 20-30 character shards of each (including the free 45 cantina and 1 every 12 minutes). And if you are struggling maybe do the 200 refreshes the closer you get to the deadline.