I would recommend:
1.
American Numismatic Society: it is more focused on
ancient coins than
ANA and it provides an excellent, annual scholarly journal and quarterly magazine as
part of the
membership price. Also, if you live near
New York City the
library is a tremendous resource. They also will send photocopies of
library materials, within reason.
2. Local Coin Club: Find a local coin club near you and join. It's
good to make personal connections with other collectors.
3. American Numismatic Association: Has more modern coin focus. If ancients are your primary interest, then
ANS should be your first join.
4.
Ancient Coin Collectors Guild: This is primarily a lobbying group trying to protect the rights of ancient and historical coin collectors from those (mostly archaeologists and "source" country governments) that challenge the right to collect such material. While I recommed
membership because this fight is important, I put it last because it does not offer cutting-edge reading or research opportunities for a
new collector.