Yes, it's a heavy lift to get jgc now but given the benefits, it is appropriate. What is your ultimate goal? Earn jgc with minimal cost/effort? Or get there the fastest regardless of cost?
I think the credit card spend is the most efficient way to earn LSP. How you decide to spend on your credit card is up to you, though there is a manufactured spend forum here if you decide to go down that path (I don't recommend but ymmv).