The first and most important "accessory" for telescopes are eyepieces. Every telescope needs a set of low, medium, and high-power eyepieces as well as a Barlow lens.
A great value is in purchasing a telescope eyepiece kit.
Telescope Eyepiece Recommendations
Budget Eyepiece Set:
25mm, 12mm, 7mm Plossls with a 2X Barlow lens.
Expanded Budget Eyepiece Set:
Add a 30mm to 35mm Plossl and a Nagler superwide. These are top-notch eyepieces for the cost.
Find your inner astronomer. Your complete guide to amateur astronomy.