It highly depends on what you know to trade.

Apple GC will trade higher than supermarket coupon.

But because second hand market for Apple GC is a lot less liquid than supermarket coupon
I strongly suggest you to trade a small amount (say $5K) (which you can easily use yourself even if you can't sell it)
with one of the traders in https://forum.hongkongcard.com/forumSE/4-25 (Apple GC will be very hard to trade ATM given there's few Apple products profitable to be traded on the parallel market)
before maxing the cards to $30K.

If you previously traded Apple GC and you confirm your trader is still active, then doing a forced trade this month is not necessary.

You can see user "NewCard" in https://forum.hongkongcard.com/forumSE/4-25 trying the same thing (establish contact with Apple GC trader) - not sure if he's getting much luck.