So save the pennies for a bigger lens.
I’ve been doing research on the internet on them.
Apparently they alter the amount of light into the camera.
Coming from a bridge camera there is so much to learn. Hopefully not financially.
They don't "alter the amount of light coming into the camera" - it's just plain physics. You have a prime lens of a certain f stop, and once you put a 2 x on, you have the same amount of light actually going into the lens, but are 'zooming in' on what there is, so you have to open up two stops. (To get the same amount of light from the subject matter, you would have to add two stops to the prime lens - that's why long lenses with wide apertures are awfully big in diameter, heavy, and expensive.)
But actually, as Taunton - OOPS, sorry EAstWestDivide - raised the matter - I found using a converter was actually WORSE than 2 stops "loss" - more like three stops, as it must have absorbed some of the light.
OF course, it's also true what he says - once you go above a focal length of even 200mm, it's almost impossible to hold the camera steady enough by hand alone - you really need to use a minimum of 1/250 second. Best to use a bean bag, monopod or tripod.