As with everything, the first thing to do is read the instructions for what you want to do, ignore all the other stuff for now.

For the web and ebay, you don't need your pics to have a massive file size so read the instructions with reference to not only the physical size, but the file size and set the camera accordingly.

If you need close-ups, a suitable camera should have a macro setting. Lighting is important, the "best" light is daylight, NOT in sunlight though.

Learning can be tough, the best way to learn is to take lots of pics and learn from the mistakes that are bound to follow. Professional photographers can take a relatively simple camera and produce superb pics with it, they've learned from their mistakes. Identifying the cause of the mistake is key though.

Although you can produce ebay pics "straight out of the camera", a photo editing program is really helpful in that you can correct a slightly skew-whiff pic or crop it so that you've not got too much background.

Initially, the KISS principle is best, more advanced pic taking and manipulating comes later.

My pic of the pound coin was initially skew-whiff and had a lot of background so I straightened it and cropped it. I re-sized my cropped pic to 800 pixels wide then reduced the file size from over 600k to just over 300k.

Depending on your camera....... with close-ups you may not be able to "fill the frame". If you're using the macro setting, if you try to zoom in, your camera may not be able to get the subject in focus, hence the fuzzy pic. Taken from further away with less zoom or much closer with even less zoom may result in lots of background (but the pic will be sharp), hence the need for a photo editing program.