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Well, you can use your eyepieces - the results may be okay in the central part of the image. Don't expect much from using the 1.5X and 3X Barlow though - they may give a decent image, but cheap ones that come with small scopes tend to be pretty hopeless.
I assume that you don't want to spend as much on an eyepiece as you did for the entire telescope, and would want good budget ones. But the budget ones will most likely give you soft edges in the the eyepiece.
Does your telescope have a 2" focuser? If so, you'd want a 2" eyepiece for low power.
The focal ratio of your telescope is it's focal length divided by the diameter of the mirror, and is usually around f5 for your sized dob. Divide the focal length of the eyepiece by the focal ratio to get the exit pupil of your eyepiece. So a 35mm eyepiece divided by f5 gives a 7mm exit pupil - which is the lowest useful power and widest field you'll get in your telescope.
Only problem is that a 7mm exit pupil is only really useful with really dark skies, and makes the image look ugly from light polluted sites like. If you're viewing from a darkish place in Mt Martha, you'd probably like a 5mm (25mm eyepiece) or 6mm exit pupil better. If you are in the built up area, you'll probably like 5mm or 4mm (20mm eyepiece) exit pupils better.
Lots of people like 3mm exit pupils for general viewing at moderate power of open clusters and galaxies. I prefer a 2mm exit pupil for galaxies.
For high power viewing of planets, 0.5mm to 1mm (2.5mm to 5mm eyepieces) exit pupils are best, and you can either buy individual eyepieces or use a Barlow magnifier lens to achieve those focal lengths. Though you would want to buy wide angle eyepieces, rather than Plossls, because you will have to push the dob around a lot and want the wider field.
You can get such eyepieces inexpensively at Andrews Communication in the Guan Sheng (GSO) section or from Bintel, or wait as they often come up for sale here second hand.
If your dob is jerky as you push it around, just apply some car wax to the bearing surfaces and perhaps some axle grease to the main screw, till it goes smoothly.
Regards,
Renato
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