Stay far away from episodes 168-189. It's pretty bad in all conceivable ways. Especially a lot of the animation. And don't worry about missing out on anything that may or may not have anything to do with non filler episodes, because the arc is completely and entirely not related to the regular bleach story at all. The filler begins with "We will now take a break from our current story and bring you somewhere else."
230-255 is another arc that is completely separate from the Bleach story, BUT I thought it was pretty good, especially the beginning half. It got a little stupid at the end, but nothing too bad. I would suggest watching it, cause I for one liked it better than anything after they entered Hueco Mondo.
256-265 I would skip. I only watched the first two episodes of this mini arc, but they were really stupid so I didn't bother with the rest.
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