Then you can spend them as soon as you get them. You can overload these hexes and then you get a large number of resources in one roll. If you have resources that compliment each other (wood and brick or ore and wheat), it may be a benefit if they are on the same number (both wood and brick are a 9). It is hard to get past the 5 point mark if you have no ore. Without ore you wont be able to build cities or buy development cards. If you wait till 5 or more, people may see you as too big of a threat to trade. Try to get ore when you are at the 4 point mark. Other players may gang up on you and not trade with you to avoid you getting even more ahead. If your Settlers of Catan strategy doesn't involve much ore, don't wait too long to get it.

But sheep are also used to buy development cards which are purchased throughout the whole game. They are used to build settlements, which is early on in the game. Ore and wheat become more valuable as the game progresses. Ore is used for development cards and cities. Ore is a close second as there are also only 3 hexes. Brick overall is the most valuable as there are only 3 brick hexes and is used for roads and settlements. This is because people get their settlements built early, then proceed to build cities. Typically wood and brick are very valuable early in the game but lose value later on in the game. You can block other players, inhibiting them to expand. Lastly, placing very last (so going first) can be a huge advantage. Especially if there is a high odds number near its resource port (8 brick by the 2:1 brick port). Keep these in mind when doing your placement. Watch other players to see if you can pick up on what Catan strategies they are thinking of doing. It is unlikely that a really good spot will be left open, especially with more players. If you are hoping to expand towards a prime stop, keep in mind the order of placements, and how many placements are left.

Settler of catan cards