My eyepiece collection started with Orion 4,5" Dob - I got 25mm and 10mm Plössls, and I started to expand it to fit C9.25, then C14 and finally Obsession 18. I have tried to cover most important magnifications and fields of view. The complete list of my eyepieces for C14 and their parameters as used with C14 are listed on CGE1400 page. C14 is a long focal length scope, so the eyepiece do not need to be extremely well corrected. I have zeroed on the low-to-middle range eyepieces like Orion Expanse 20mm and 15mm and Orion Optiluxe 40mm. They worked really good, and they were the most used ones. I bought TeleVue Radian 10mm and Orion Lanthanum 7.5mm for high magnification views, as well as Orion 2x Shorty Barlow. Radian 10mm was most used for planets, seen was never good enough for 7.5mm Lanthanum.
After a while I realized that I miss medium focal length wide FOV eyepiece, just around this time Williams Optics released their UWAN series of eyepieces that got raving reviews and were reasonably priced. I bough 28mm UWAN (82º apparent FOV).
When I bought Obsession 18" Classic I knew that most of the old eyepieces will show aberrations with this fast f4.5 scope. I needed wide field medium focal length eyepiece, and again, just around this time TeleVue released their Ethos series, with astonishing 100º apparent FOV! First I got 13mm Ethos, then 21mm. Both are fantastic eyepieces, and in tandem with 28mm UWAN covers all regular deep sky viewing, while Lanthanum 7.5mm and Radian 10mm are used for planets and the Moon. What about Orion Expanses? They don't look that good anymore - there are aberrations at the edge of the field, but they work very well with my binoviewer. Binoviewer requires 1.6x Barlow to focus and at that focal length they work very well - and are cheap enough to buy in pairs. Lastly I added to my collection Celestron Lumicon 15mm (82º apparent FOV). It provides higher magnification then 21mm Ethos allowing for better contrast with faint objects and more details in small objects. Details about eyepiece parameters and use with Obsession 18" are on this scope's page (bottom). To correct Obsession coma I started to use TeleVue Paracorr.
It is also a good idea to have some eyepiece boxes to transport them around. I got large Orion Eyepiece Box, visible on the top of the leftmost picture above.