Aha! I think I've ha a different approach on things.
I mostly shoot live music which means a lot of movements under difficult light conditions, so most of the pictures are rubbish, usually 10% are worth working on. I import all pictures in a catalog "Rockband X" and when i go through them all i sort out the 10% worth keeping in a collection called "Rockband X". But sometimes I wanna go back to the catalog when developing pictures, hence my question.
I always thought that collections is the place where you keep the good stuff, not hundreds of hundreds of pictures that aren't bad enough to go to the trash but not good enough to show to a client

but any tips on how to organize in lightroom are welcome!
These are just suggestions
take them, ignore them, or better yet
modify for your usage.
Pop all the shots of gig into the appropriate Collection. In my system I would have a Collection Set for the band. Inside the Collection Set I would have Collections for each date. That way you can see all the photos for the band regardless of date by clicking on the Collection Set, or you can zero in on a particular date.
After putting all the photos into the Collection start with the 1st photo and scroll through all the photos quickly making one very quick decision. Keep it or not? If it's a keeper it gets 1 star. If not a keeper, it doesn't get a star. If you have to think about it, it's a keeper for this step. Go quick
don't think. Essentially, anything that is not immediately worth trashing gets 1 star regardless of how good it is.
Now filter the collection on 1 star or greater - the duds will drop out. Do the same thing again with these images
move quickly and without thinking too much. Is this image worth spending any time on? If it's worth at least a little time
it gets a 2nd star. Move quickly. One finger on the arrow key, the other on the #2 key. Just zip through.
Now filter on 2 stars. A large number of your images will have dropped out by now
perhaps the majority. Ideally, these two rankings took less than 5 or 10 minutes
perhaps less than 2 or 3 - depending on how many shots you typically take. You are now only looking at - at worst - mediocre shots. Now you can spend a bit more time looking at each shot. You will have a good sense of what the complete collection looks like. You will know if a particular shot is the only one of that person, or if you have a dozen to choose from. Start promoting the images worth spending time on to a 3 or 4 star ranking.
Perhaps use the colour flags to group images. I use Green to show that I am done editing the image
there is nothing more to be done. It may still only be a 3 star rank, but it may be 'good enough' for a particular use. Other images that I would use in a portfolio situation will be 5 stars. Yellow means I have started to edit, but it's not yet done. Blue I use to quickly group images from a several Collections together. You can set the colours (except for Purple) using the number keys. Green is #8 for example.
Use the filters to group images together temporarily. Use Smart Collections to do the same thing (plus more) for more permanent groupings. For instance you may create a Smart Collection inside the Collection Set for a band that shows all the images ranked at 4 stars or more and with a Green flag. Then instead of clearing and setting the filter for that Collection Set each time, you just look inside the Smart Collection. You could create a Smart Collection that shows just 4+ stars, and then you filter those images by colour flag to see which images you have started to edit - but haven't finished. You can select more than one colour flag so you could have the 4+ Smart Collection, and you can see the done and almost done 4 and 5 star images.
Lots of possibilities.
You could have a Smart Collection that shows all the Green and 5* images from all the bands. You can right click (or Ctrl click) on an image to find in which folder or Collection that image lives in - to help you locate the other not-so-good images that go along with it.
Hope this helps.