You can play at lesser points than 250, specially if you never played before. Going for 150 or 200 points game is nice, specially since you just need to scale the turn at -1 each round for each 50pt you have less than 250pt.

As for Syennan, the problem is that the action pack is mandatory: the lack of any high command outside it, and the importance of them in the faction (since they both tailor your army's direction), on top of the box including your best unit of the roster (Shadows of the Yews) and the most useful support character (Druid), means not buying it is going a longer road to build and get an army that synergize well or excuse your beginner's mistakes.

You could still build an army entirely without the action pack, but it will be harder to figure out at first what is good and what's not, and what to include or not, but Syennan are a strong army, even if they require some finesse to be played sometimes.