I am using 'GPSLog WinCE' with a Dell Axim Adv. The Program is free, but you
have to create your own maps (or select one of the available maps). So you
will have to learn a little bit about how theese maps are organized.
GPSLog WinCE is easy to use inflight, it propably has all features you need,
and there are Windows programs for normal PCs, which can be used for
evaluation and training on your home PC.
So it is really worth to try this program!
You need a GPS receiver with a NMEA output and a (fitting) cable.
I would not spend too much money for a used IPAQ.
Before you spend a lot of money for other gliding software it is a very good
idea to try Henryk Birecki's programs.
Anyhow: never use a system inflight, if you are not very well trained to use
it perfectly. The best way to learn is to fly in the back seat of a twin
glider and try how to use it!
Best regards
Walter