I recently have been doing a bunch of research on this lately so I think I can be of some help.
by exlaining the function of each bag, it shoudl make it much clearer what their use is and if you can get away with using less.
220 micron - trash filter - ABSOLUTELY NECESSARY
190 micron - trash filter - only needed if you want to be super clean
160 micron - trash filter - use if you want really clean bubble
120 micron - food grade, sometimes bubble - I consider this one necessary, cleans up the 90 micron or 73 micron SO much that it allows it to truly bubble.
90 micron - some people love this more than 73 micron, I don't consider it absolutely necessary for dank clean bubble, but if you are getting into hash connoisseurship, you would be better off separating the 90 from the 73.
73 micron - the gold bag, the dank, usually. if you're using the right strain this bag usually results in the highest grade product, or the 90 micron will be the highest grade. either way, THIS BAG is essential.
45 micron - medium-high grade after-catch of the 73 micron, this bag is worth it if you want to get as much smokeable product as possible. I personally haven't bought one YET, I consider the 73 and 90 microns to have higher priority, I just use the 25 bag as the last.
25 micron - food grade depending on strain, sometimes bubble with sativas or certain oily strains - catches pretty much everything worth catching in the smallest micron, I use this stuff for edibles usually. but it's certainly smokeable if you're not picky about quality.
I've grown to feel the chime of many other hash makers "if it don't bubble, it aint worth the trouble" seems to really jive with me. I still smoke herb but if I'm smoking hash it better be full melt.
here's some 73 micron Lush (Lemon Larry OG x Old School OG x Chem D)F3
