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The faster the focal ratio as in an f5 is faster than an f10 the harder the scope is on lower cost eyepieces designs.
The light cone becomes steeper at f5 and 4 or 5 element eyepieces have difficulty in keeping stars in the outer field corrected if they are quoted as wide field design..
Meaning that for example the $150 Andrews 5 element 30mm 2" barrel 80deg (wide field) works well in an f10 and reasonable well in an f6 - f7.5 but has only about 60-70deg field out of the 80 degs with very sharp stars at f5.
Meaning stars towards the outer edge become elongated.
So for the price you just accept that it is only a 60-70deg eyepiece.
Some people can accept this considering the cheap price , but others who want perfection will go for the mega bucks Naglers (several hundred $) with there better corrected outer fields.
This is just one example and there are many others to consider when buying Eyepieces.
Do you where glasses for viewing?
If so you also have to consider a thing called eye relief.
This is the distance you have to have your eye from an eyepiece to see the full field of view.
It varies greatly form focal length of the eyepieces to designs .
You will have noted this with your set you have now the difference from the largest down to the smallest focal length.
As you are only new to astronomy and telescopes I would not rush out to buy eyepieces now as you have a good starting range. Get a 2x barlow and leave it at that for a while and see if you are still interested 12months down the track.
In the mean time try to find some one in you local area with different eyepieces that you can try in your scope.Go along to a club if need be.
Hands on is always better than word of mouth when it comes to eyepieces .
Word of mouth just helps to narrow the large variety in EP's down.
Mark
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