These longer treks are ordered by difficulty and are predominately camping treks. Tsum Valley is the easiest and the Manaslu Circuit, both of which can be done as tea-house treks (that is with accommodation provided), is on a similar level to the mid-length Annapurna Circuit, perhaps half a grade more challenging, as are the Upper and Lower Dolpo treks. Then comes the 3 Passes Trek (which can also be done as a tea-house trek). The Makalu and Kanchenjunga Base Camp Treks are strenuous treks, which take you across some higher passes. The Rolwaling trek is more challenging and only to be attempted by experienced trekkers.
If you want to upgrade a stage try a trekking peak.