Pool / block "Effort" and "Luck" are different names for the same thing. We prefer to call it effort, as it is more descriptive. Block effort refers to one block only, overall/pool effort refers to averaged last block efforts. Current effort refers to block that is being mined right now (real-time effort, so to say).
Effort is measure how many hashes our pool made to find a block. If a block was found exactly when predicted (based on global hashrate, pool hashrate and block time/difficulty). Each block has its own "luck". Longer block = higher effort. Efforts more than 100% means we were unlucky, efforts less than 100% mean we were lucky and found a block sooner than expected.
If the pool functions properly, the overall effort stabilizes and stays around 100%.
Pool having lower/higher effort does not tell about its quality or future luck!
Mining is very unpredictable, and sometimes we may have few blocks in a row with high effort (even as high as 300%+). This is normal and expected. We can also get a few blocks with extremely low effort. So the short-term incomes may vary. Again, if you are mining for a long time in the same pool, you are only concerned about the overall averaged effort.
Edited by Wor3d