What is the best way to get the Avarice conquest?

The surest way for now to earn the cheevo now is novarg's answer. You will need 100 TX bags. Note however you need to unequip your pet, stand next to your stash so you don't move (100 bags won't fit in your inventory all at once), and just pick them up all at once after you open all 100. Also, the bounty gold amount is unaffected by gold find, and is fixed, so you need 100 regardless of how much GF you have (you can have less if they are higher bags than TX, and more if the torment level is lower).

The following no longer works due to gold barons being nerfed in terms of the amount of gold they drop.

The easiest way for me was to find a gold baron on t10 and then put my paragon points into gold find and wore a leorics with an emerald in it. That was enough for me to get over 50m in one go.

Granted this is significantly more dangerous on HC mode if you are not properly geared for it.

You can also ask friends and clan mates who are playing on t10 to keep an eye out for gold barons.

I found this on reddit, link

This is a quick guide covering how to complete the Avarice conquest (50 million gold streak).

This method took me one attempt and I had room for another 10-20 million. It goes without saying this is done on T6 and you will need boon of the hoarder. Mine was 28.

Gold find: 9000% ish. Sun keeper, Gold skin, Leoric's with emerald, paragon and 80% amulet should help you get there but I did it without Leoric's.

Where to prep: Ruins of Corvus and the area that connects with it.

You will need to run around getting as many scarabs (and other mobs) spread throughout Ruins of Corvus. Do not kill them yet as the gold piles will despawn over time. Make sure there are several monsters right by the stairs because you will need to keep the gold streak as you change maps (it lasts for around 3 seconds).

Prepare the other area the same way. When you reach a dead end you will start to back track while killing monsters and getting the gold as you move along.

Take your time: Don't pick up every pile as they drop. Make sure there are monsters ahead before picking everything up.

If you can't see any, grab 1 pile, aggro a couple of scarabs in between populated areas, go back, pick up another pile to maintain the streak and then kill the scarabs. This is not about speed, it's about coordination.

You will need to be quick when transitioning from one floor to the next as you have 3 seconds to zone in, kill some scarabs and pick up another pile.

Should you try this, good luck!

I know this is an old question, but I'll add my two cents.

Probably the easiest(and most time consuming) way to get 50 mil gold streak. I did equip some gold find items, but they don't seem to have (much) effect on the cache drop. Anyway, I collected 110 caches(including bonus caches) and opened all of them together.

This gave me 57 mil gold(around 1:55 in this video).

Of course, as l I said in his answer, if you face a Gold Baron while hunting bounties you can get this conquest there, but even if you fail you can still just continue collecting bounties.