I'm having a hard time coming up with a list of packs I'd recommend to new players to start with that wouldn't break the bank and offer some value. The must haves, in order, in my book at least would probably be:
2) Secrets of the Artificers
3) Epic Destinies
4) Expansion Pack
5) Vault of the Artificers (house c challenges)
Vale and Secrets together will gear out essentially any character for faerun, but you want to start earning destiny xp the moment you hit 20 so get destinies before the xpack proper.
If they had a little extra TP in their forseeable future I'd probably recommend Carnival and Red Fens as good (and cheap!) early packs to buy before they get Vale.
To be honest, I'm quite happy I already own all the packs (and the xpack), as it would be much harder to get started now than it was a year ago. Before, you needed Vale of course but you had the option of sprinkling in a bunch of cheap packs whenever you wanted. Everything in the top 5 list above is around 1k TP, which is brutal.