A lot of people like the fresh start. It is cool because everyone starts at the same time with nothing as if the game just launched. Some people level in groups, some go alone. The nice part is everything rolls over to non-season after the season concludes. This way, you do not lose anything after the season ends.
Some players are up in running T16 in an hour or 2, some take 6-8 hours. I usually hit it in the 2-4 hour mark. Go at the pace that is fun for you.
This season start leveling should be real easy now that the Altar has returned. The second node you should unlock is “Anointed”. It will make all items usable at level 1, including level 70 items. Simply get to level 18, then farm some bosses until you get 2 diamonds, then upgrade them to flawless at the jeweler.
Once you have a full set of level 70 gear, ez breezy to level 70. After that do the Seasonal Journey (hit “shift J” in game) requirements to get through Chapter 4, then get the free set from Haedrig’s gift for your class. That alone should get you to T6-10. At that point, gear starts raining from the sky, so getting the rest of the build is pretty easy.
Everyone does 70 their own way. Some are more efficient than others. I always suggest to do it the way that is fun for you. Here is how I am going to do my season start, not the most efficient, but should be 70 in less than 2 hours and have my Haedrig’s set by 2.5 hours. This is how I did it:
Do challenge rift for mats
Always play adventure mode, not Campaign
Set difficulty to normal or hard
Level up merchants
Craft yellow weapons up to level 18
spend shards to get a legendary with a good
Run to get cube stringing a few kill streaks on the way (usually level 10 by this time)
Do massacre bonus’s in some highly dense areas to get to level 18
Farm easy bosses that are bounties to get quick gems (you need to diamonds)
Unlock nodes 1 and 2, make sure to choose “Anointed” for all items level 70
craft level 70 gear starting with weapon, offhand, and jewelry, then make the rest
Turn up to T6, and do bounties for the Haedrig’s gift (In S28, think I was almost 70 by this point and about 1.5 hours in)
Finish the rest of the Chapter 1-4 requirements
Farm remaining build pieces on the highest difficulty you can kill fast to get rest of your build by doing some visions.
As for using mats at level 70, I use shards for armor and offhand, upgrade rares in the cube for weapons and jewelry.
If you decide to play seasons, good luck, and have fun