1) what is a good or average d/load speed?
Depends on your line speed? I have a 512/128 ADSL connection and my max is about 52kBps down and 13 kBps up.
What is your line speed?
2) how canI increase my d'load speed?
Depends on which client you are using, I recommend ?Torrent
http://www.utorrent.com/Turn off DHT if it is enabled this will only slow it down.
Set your upload limit to about 80% of your max upload speed.
Forward the ports if you are behind a router or similair device.