If you have installed the DG4Sybase then you do not need to install any Sybase software.
The information requested during the install is used to created a init<sid>.ora file which is thne used by the gateway to connect to the Syabse database.
You can put in dummy information and then manually change it when the install is completed.
You also say you have installed Dg4Syabse 126.96.36.199 but it would be better to install and use the latest 188.8.131.52 version as suggested by Klaus in your other thread -
The latest software release is currently 184.108.40.206 and it can be downloaded (and installed from scratch) from "My Oracle Support". Just open the Patches & Updates section, look for Patch 10404530: 220.127.116.11.0 PATCH SET FOR ORACLE DATABASE SERVER and make sure to choose the platform you want to use. Then check out the readme as it lists which of these download CD's contains the gateway software.
BTW, the CD contains DG4ODBC and DG4SYBS and it is up to you to decide during the installation which product you want to use.