How to level up Scythe faster ?

Go to Ashlands and reach the well area as shown in the below image
Jump into water and reach the top through the demonic growth.
Jump down and reach the top again. Do this like 6 - 8 times, just don't do it too many times as more riders spawn and the game will freeze/crash.
Once you spawn enough riders, lure them into the cave as shown in the image
Use Death Rage attack Alt + Right click

Repeat this a few more times once you kill all the riders. Not only you will level up pretty fast but also you get more souls in a short time.
This method is not that useful for Tremor Guantlet, go for spiders room in Iron canopy to level up the guantlet.