Given everything I said about common used and mint stamps, here is my opinion on how you should go about building your collection. This same logic applies to common plate blocks too. This is meant to save you money.
Start by buying packets of stamps or other stamp collections. When buying in bulk like this, youíre going to pay much less per item than if you bought them individually. This is a great way to buy stamps if youíre just starting out in collecting and you need many items to get your collection going.
As you buy material, there will be fewer holes in your collection. Buying more packets and collections will only add to your duplicates. At some point, youíll be getting more duplicates than new material. If you have others to trade with, great, this will get rid of your duplicates. But if you donít have any easy way to dispose of your duplicates, itís time to shift gears. You need to switch to packets and collections that have more specialized material that can contribute to your collection.
After you built up your collection and packets or collections arenít helping any more, now itís time to visit a dealer and start making individual purchases of specific items.
Buying packets or collections means that youíre doing a lot of the work. Youíre removing the items from the mounts and transferring those items to your own collection. Youíre talking to your friends to trade away your duplicates. Thatís work that the dealer doesnít have to charge for. In the end, youíre building your collection at a reduced cost at the expense of having to take your time and break down the packets and collections.
Buying packets and collections isnít for everyone. These are tens, hundreds or thousands of items at a time. Used stamps may be bought in this quantity for a few dollars. But for mint stamps or plate blocks, the buyer is going to have to come up with several tens of dollars or more. If youíre on a limited budget, you need to save your money before making larger purchases like this. Or you have to buy items individually, a few at a time, to suit your budget.
If possible though, I encourage you to buy in bulk first. Then move to individual purchases as needed. That will save you money in the long run.
Never forget that stamp collecting should be about the enjoyment of the hobby and not about monetary returns. This is especially true when youíre dealing with common/inexpensive material which is very unlikely to ever yield a monetary value greater than your cost.