Look, I wouldn't bother using a TC with the 55-300.
AF is grindingly slow and hard to lock focus, and you're just losing far too much light at 300mm.
If it means a lot to you, but money's tight, consider a manual focus mirror lens - 500mm is the common focal length of these lenses.
If you're bent on something AF, I'm afraid these don't come cheap, but if you're going to be taking chances with a TC on the 55-300, then try the
Tamron SP Pz-AF MC4 1.4x TC.
I've tried it on the 55-300 and its performance is abysmal. Now on my Tamron 70-200/2.8, it performs absolutely brilliantly. So the 55-300 is not very well suited to having TC's plonked onto it...