The above is good advice for DM/PMs, but irrelevant for the OP who will not be upgraded on his/her ticket.

The more I read this thread and think about it, the more I'm annoyed by the original question: someone who has apparently flown DL on one or two domestic trips this year asks about upgrading a super-cheap TATL ticket (not eligible for upgrades) when he or she doesn't even the miles that would be required to upgrade from a much more expensive fare.

This might be a very naive question from someone who claims to fly a lot, hoping for a too-good-to-be-true answer, combined with a hidden implicit solicitation to buy/barter upgrade instruments.

Alternatively, it might be a display of extreme entitlement: What would be the business benefit to DL of upgrading the OP rather than perhaps one of a hundred others on the flight who are also SkyMiles general members travelling on very cheap tickets, not to mention perhaps fifty with DL status who would also like an upgrade?