Quite honestly there is such a lot of misinformation written and talked about cartridges it would make a book in itself.
So, beginners guide to cartridges.
Fact 1. There really is not one bad cartridge out there at the moment, they will all do what they are supposed to do if we point them in the right direction.
Yes some will do it better, that's what we have to find, the one that suits us.
Fact 2. Dirty cartridges, wrong description. The 'dirt' is unburnt propellant or residue left over from the burn, more noticable in cold climates, but not really an issue non-corrosive not harmful to the barrels, if your happy with the cartridge performance don't worry about 'dirt' it's gone with the next passing of a wad to be replaced by new 'dirt' clean when you get home. Never had a complaint about black powder dirtying barrels and that is filthy stuff and corrosive.
Finally, Fact 3, find a cartridge that suits your pocket and that suits your shooting style/ performance criteria and stick with it . If you are happy with it's performance and it suits you and gives you confidence and breaks clays stick with it, it becomes a Constant. If you then go through a bad patch you know it isn't the cartridge.
Example, I love Clever and RC cartridges, have total faith in both brands, but I do struggle to get them locally to me.
Express & Eley readily available and all of them exceed my shooting ability, yes you will find one that you don't like, so move on.
When you are out shooting at a ground have a look at the spent shells lying around, it will give you a clue to what is popular and readily available locally.
Locally for me Eley Olympics are the best value cartridge available.