Here's what I've been doing to get my first char going (solo) each season. there are slightly faster ways but they're boring AF, if you have any suggestions tho feel free to post.
create a new season char, exit, do the challenge rift (don't do one for the week before season starts), save bag on new season char
do all the bounties once (you need this for journey anyway, start with bosses to get a few rares) then rifts to lvl 34
at lvl 34 spend shards on wrists, if you get Warzechian Armguards pop the cache you got from challenge rift wearing them and pick the gold (you'll gain 10 levels) either way continue to lvl 40.
at lvl 40 max blacksmith (using DB from challenge rift bag) and try get a 2h (non class specific) with anything Chance on hit on the secondary mods (this eliminates 6 of the 10 possible rerolls and gives you 1:4 (1:3 if it has life on hit on the primary;) chance of lvl req reduction)
reroll the other secondary mod to get -lvl requirements (30 is max) if it gets too expensive you may wanna craft a new one
Ruby in helm, blah blah => lvl 70.
from there it's pretty easy just focus on getting your 6 piece set first and solo a 45 asap so you can do T10 public rifts