I wanted as much available as possible to find those hidden gems, without having clutter. I guess I'm between the 'everything' and 'select hundreds' as I started off with a complete set of over 20000 across loads of platforms, then spent many months removing clones, mahjong, regional variations, indistinguishable hacks and variations to what I call a 'concise full set'. I'm now happy with what I've got and being a perfectionist, painstakingly went though re-naming roms, screenshots and FE lists, unzipped and recompressed roms and shrank screenshots down. I've now got a selection of about 8-9000 across about 15 platforms with no duplicates or stupid appendations like '[!], [G], set 1' etc.