I farm my own tree cuttins > grow sapplings (100% as long as you do it right) > either sell sapplings 600k-800k stack or try growing elemental ores. Cheapests ores sell about 600k each and most expensive ones go 1.5mil +.
But you said cuttings are over farmed ... hmm. Another option is fishing. Boring as it is, I've caught quiet a few fish that are 70+ levels above me when i have been skilling up. I've been borring a friends lu shang, but moat carp sell pretty good on my server. About 15k/stack. I've been on the ship to mhaura before and people pulling in lots of high gil fish. Gigant Squid 15k each are one I see a lot.
Spiderweb farming maybe? A few people in my LS farm lizard skins in crawlers nest on the higher level lizards.
I've been known to check the AH price for high cost items and bid a little above 10% of the cost. This will catch the people that forget to add a zero. HQ Fire Staff selling for 6mil -- bid 600-700k on it. Try on a bunch of high gil items. I use to avg. about 1 item a week where I would make a few million gil profit easily. May be kind of rude, may piss the person off. I only had one person send me a /tell about getting their item back. I got my Serene Ring for 2.5mil

The first tell that person sent me said "You son of a bitc* -- give me my ring back". If someone just gave me a sob story I would probably give it back if they give me a little gil afterwards ... but called me a SOB when they are the one that screwed up ... sorry lol.
Buy and resell dynamis currency. 1 unit goes 100k -- 100 unit goes 10mil right now on Ramuh. I've seen people selling 1 unit 70-90k and 100 units for 9mil. Grab it and resell for higher price if you can. Might take a few days but will eventually sell.