I share your thoughts about non-availability of few applications for N9 but it is a great phone for what it offers. You shouold have thought about it before buying it, done some ground work or read some blogs regarding availability of apps you require on it.
Anyway I can help with your gtalk. You can chat using gtalk, it is inbuilt on the device, you need to add your google username and password via Accounts > add account, for making video calls you need to install 'gtalk video call' app from Nokia store.
If a reply has solved your problem click Accept as solution button, doing it will help others know the solution. Thanks.