I am pretty sure there is only 1 legal Ambipom in that format. The current one is really situational but can hit for some pretty huge numbers with a double colorless and a bunch of cards in hand.
[spoiler]
There are probably a bunch of ways you can boost this guys potential. I would suggest putting a bunch of muscle bands/silver bangles in the deck for bigger numbers on the 2nd attack. Also 4 double colorless are almost required. Any cards like Cheren that boost your hand size is adivsed. Sadly he is super frail but he is stage 1, so he can easily be put on the field without rare candies. The deck will lose all its speed if your opponent uses the card N to get your hand size so a rather lower amount, so its kinda risky but high reward and satisfaction if you can pull something like this off.
This is just some random tech I thought of, but there is a (Normal not EX) Virizion in this format, that when it attacks it gets 2 cards in your hand. Which is pretty decent for Ambipom's 2nd attack
[/spoiler]