I'd say Generation are as good as any of the relatively inexpensive ones to start with. As mentioned, probably the most versatile key to buy your whistle in would be D if you will be playing mostly Irish type stuff. Start playing with your left (or upper hand) closest to your nose and practise whenever/wherever you can. I knew of a guy once who drove a cab and used to practise between fares. This guy was so dedicated. One day he got robbed and the thieves locked him in his trunk/boot while they made their get-away. He actually practised till the police came and let him out. Passers-by heard the whistling coming from inside the trunk/boot of his cab. True story.