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In terms of eyepieces for a 10"/F5 Newtonian it's not easy to get something that works well in such scopes cheaply but there are some good options still.
Poor quality eyepieces have lower light throughput so the image will not appear as bright, some will have off axis astigmatism and field curvature which means the stars will not be pinpoints, but have tails or appear elongated as you get further away from the centre of the field of view. In many cases they also have shorter eye relief, which means you almost need your eye squashed onto the eye lens to use them, which makes them less comfortable to use.
Many eyepieces will not work all that well in an F5 Newtonian. The main issues are the steepness of the light cone due to the fast F-Ratio of F5 and the inherent coma of the Newtonian design. Some people on this forum will babble on about the curvature of the focal plane not being suitable to certain eyepieces, but this is essentially irrelevant as the focal plane on a 10"/F5 Newtonian is pretty flat, but not quite.
You can certainly get started with the eyepieces supplied with the scope but plan on adding some better quality ones fairly soon.
Some people are happy using middle grade Chinese / Taiwanese eyepieces like Baader Hyperions etc, in an F5 Newtonian, but I am certainly not, as I still find the edges pretty soft.
Without spending the earth (that can come later when you know you're in for the long haul) You basically have 2 options. You can buy eyepieces like the Japanese made orthoscopics which have short eye relief and a narrow field of view, but give excellent image quality, or buy some of the discontinued eyepieces like Vixen LVW's or Televue Radians. These deliver excellent image quality, have long eye relief and a wider 65deg and 60deg AFOV respectively. These come up 2nd hand on various internet websites fairly frequently and you can pick them up for about $150 each. To get the same image quality and ergonomics from a new eyepiece you will spend over $400 each.
Cheers
John B
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