Note there is a similar post here about "Which set should I do next" And then there are many answers and some the same and some different. Here to I would suggest you just try collecting all coins. The sets will happen when they happen. If you consentrate on one type you may loose some great deals on something you do not collect. For example if you focus on Quarters and someone has a pile of Mercury dimes for a great price, you may ignor that and loose out on great deals. I say if for moderns, go with as many as you can.