We've all played the game where a building costs 8 Wood and 4 Stone to build. Even the classic computer game Starcraft had two costs — minerals, and vespene gas. Why?
Having these two separate resources doesn't really achieve anything, except making things a bit more complex to afford.
Each resource should have its own fundamental identity, tied to some very important game concept.
In our wood and stone example, maybe wood buildings produce resources, while stone buildings are worth points. This actually means something now. As a player, I don't just want to get more resources. I want specific resources, depending on what I want to do. If you have resources that aren't fundamentally different, you should probably merge them. Even in this example, wood and stone are fundamentally both just different building resources. This would be fine, if building buildings was the central part of the game, and each one of those two resources could be given an individual identity within that.
Unless a game is about resource conversion, no resource should be easily convertible to another resource.
"Block" is a common score I see in combat games. It reduces damage. Yes, it's different to some kind of damage score, in that it's defensive, but it's so clearly equivalent to the attack score, because both are part of the game's combat system. Also, it's boring.
In my gangster game, there are four clearly distinct resources. There's health, which keeps you alive, and in the game. There's money, which buys entry into powerful places. There's rep, which wins the game if you get 10, and there are gang members, which cause you to do more damage to opponents. You could argue that your health and the opponents' gang members are related concepts, but they're not that close. The resources in this game all correspond to different systems and concepts.
Wingspan is a great game, but it has its flaws. Some bird cards will let you tuck cards underneath them. Others let you put food tokens on them. However, tucked cards and food tokens are all simply worth one point. These two systems are usually identical. I would've made the placed food tokens usable by lots of other birds, or have some rule difference. Or, I would've just abolished the tucking of cards, and just used tokens some more.