I'm a glider pilot myself, with about 75 hours now.
In terms of ASI markings, the glider I usually fly (an unflapped 15m machine) has exactly one marking, which is a red line at VNE (135kts). VA (or whatever the max maneuvering acronym is) is 108kts, but isn't marked. Stall is ~38kts, while thermalling speed is 45-50kts. Cruise speed is lift-dependent, a varies from 55kts upwards.
The "full" set of markings typically seen in a glider instrumented in the last 5-10 years would be a green line from some factor above stall (1.2?) to max maneuving, then a yellow line to VNE, where there'd be a red line. There's usually a yellow "pointer" at best unballasted glide.
Some pilots of flapped gliders will put a ring round the ASI with markings for the "best" flap setting for each speed range, but this varies depending upon how much ballast is loaded.
To be honest, when flying my ship (which is not a grob103 despite my moniker) I only glance at the ASI occassionally - wind noise and control feel are much more important, and when cruising between thermals I have a vario to make annoying sounds at me to speed up or slow down.
I've got a good photo of a recently purchased glider panel layout if anyone's interested.
Flap setting will markedly affect stall speed.
Cheers,
David