With decent gear that has the right rolls and a few paragon levels, you should be able to do GR100s without a problem on the UE multishot build. At lower levels, you should focus more on improving your gear and gaining more paragon levels (paragon 800 is considered a good base because after that all paragon goes into main stat) and increasing the main gems that you use for the build (Levels on your bane of the trapped / Zei's etc are a huge part of your damage). All the builds in the game can reach GR100 reasonably easily these days. This is personal preference, but I would say that you should not be augmenting with gems that are lower than about level 100. When should I start augmenting? This season I've cleared a gr80 in 6:30 with ue ms dh but I'm switching to natalyas rapidfire, at what lvl legendary gem should I start augmenting?(My highest right now is 40 something, I'm paragon 570-580 approx.).Augment your best items first, and work your way down from there.

You don't want to spend your gems augmenting an item to have a better one drop a few rifts later. Make sure that the item you are considering for augmentation has the correct rolls, and that those rolls are at least close to being max level. Before you augment an item you should evaluate if it is worth spending your gems on (both the actual levelled gem, and your Flawless Royal gems). This does not mean that just because an item is ancient that you should augment it.

Augments can only be placed onto ancient items (including primal ancients). Does it work on non-ancient set items?(I think the guide mentioned you could, but I'm unsure)?.Most people will augment an item a few times, generally, it is done when you have gems that are about 20 levels higher than the augments currently on the item. The new one you put on an item will overwrite the old one, be it a higher or lower level gem that you are augmenting with. Yes, you can augment an item as many times as you like, but the item can only hold one augment at a time.

Can I augment multiple times? Like if I augment a primal with a lvl 50 gem but I get a 70 later on, can I 'upgrade' the augmentation?.

Augment ancient items in diablo 3