wcSyndrome
Maybe cheating a bit but there are several genres of games that are named after the games that popularized their mechanics such as roguelike/roguelite, souls-like, metroidvania
You'll actually pick up silver leaves from each stage of altars of sorrow and more at the end so that works out if you're going with that option. Otherwise they drop from any activity completion so I wouldn't sweat farming them too much
Altars of sorrow are pretty nice since there're plenty of ads and most fall over to any damage. Onslaught is also fun and you can earn some pretty great weapons (don't forget to attune at zavala if you want to target something). If you don't want to compete with other players then the opening of grasp of avarice is also pretty quick.
Overall would recommend weaving in solstice bounty completion with other things you're trying to get done (catalysts, event challenges, etc.) since farming almost anything like this can get monotonous
Do you mean unlocking dual destiny is ambiguous or farming additional drops of exotic class items?
I've been alternating iron banner, finishing post campaign minor quests (mainly Micah's storyline), and chasing various loot from older content. I took some guardians through grasp of avarice and deep stone crypt recently for their first times and that was pretty gratifying.
The chocobo race is absolutely brutal, best of luck