i honestly only recommend doing seasonal conquest for stash. the guardian for that potrait hardly seems worth it. you can barely tell the difference other than the leaf color :/

I got that avarita by accident doing bandit shrine on t13 thanks to 2 or more gilded goblins ^-^; hardly wore any gold find gear too.

cosmic wings is not recommended for people with little patience. i've been farming for 3 weeks already with minimum 4-6 hours with a 4-6 rainbow goblin per session roughly 1 rb per hourly farm + friend/random group rb invites, and still haven't found princess lilian. only 2 princess stardust :{

very frustrating ;_;

i like necromancer, but i'm rather skeptical about it in regards to the pricing, and lack of additional content to go with the class. example in LOD d2 we had 2 new classes wasn't it and a few new acts to the story. that was rather fun. But with d3 all we get is a new class, and possibly a new quick gear gear wardrobe mechanic, thats it :/ and i don't recall them even talking about price.

grift isn't really cutting it for me, because unlike hearthstone and heroes of the storm which give you rewards for being in top bracket, it doesn't seem like theres anything for diablo grift ladder as far i could see. i got to top1000 solo sader for s9 at one point.

A friend of mine also got onto rank 500 ish solo grift on HC on quite a lower grift cause not enough people bother playing that lel....
anyway other than cosmic wings and seasonal stash, my other recommendations...

- falcon wings (mysterious chest)
- transmogs (mysterious chest. Note that each new season have to find again.... so only bother if you non season doesn't have it yet to even be worth the effort)
- rainbow potrait (whimsySHIRE from sir william. need staff of herding, i did this on non season so i didn't have to farm another. i could still use the potrait reward in season no problem)
- harvest penant (from a unique khazra in A2)
- wings from doing completing the set dungeon
- diablo 3 anniversary event for butcher and cow pet, etc..... event ended so now you got to wait next year if you missed it 
- goblin menagerie pets
- kill ravi in A1 to get a rare zombie pet
d3 to me is dead. waiting on d4 and hope they have the sense to be competitive against lineage eternal and lost ark which is what i'm more impressed with