The most commonly used eyepieces I use on my 8" f6 are:
- 33mm Williams Optics SWAN
- 12.5mm Meade series 4000 plossl
- 9.7mm Meade series 4000 plossl
I also have a 7.5mm, 5.5mm and a 26mm but would really like to add a 15-20mm.
My point is that the top three sizes cover about 90% of my observing and IMHO are a good basic set of sizes for your scope, however, the choice of brands are up to you.