As said above the Bounts arc is probably the best filler arc, i quite liked the new Captain Shusuke Amagai arc as it spent more time in the soul society instead of just following Ichigo all the time. Didn't think much of the Zanpakuto Unknown Tales arc and haven't even watched the Gotei 13 Invading Arc. I'd definitely recommend skipping the Karakuraiser and most of the individual filler episodes as they're just painful, there is some filler episodes with backstory for some of the arrancars which would be worth watching.
The
wikia site is very helpful in seeing how many filler episodes there are, around 155-160 epsiodes of filler, that's almost half of the entire series so it all depends how much time you want to spend watching filler.
Personally if i started watching from the beginning again i'd just skip all the filler episodes and go back and try the big filler arcs afterwards. At least then the filler wouldn't stop you from watching the rest for quite awhile as it's happened with Bleach & Naruto with me.