Afaik, tubes come in different lenghts, and ideally you want to be close to half the focal length of the lens you want to use. Some lenses work well with tubes, some don’t, do some googling.
The expensive ones have electronics in to communicate with lens and body for autofocus or aperture control. However a cheap option might be to get a cheap old manual focus prime, with a mechanical focus mechanism and aperture ring, then a ‘dumb’ tube which are only a few quid on ebay. However you may not get enough change out of £80 to make it worthwhile doing that.
If you really want to get into it then a tripod with a tiltable centre column like the Benbo Trekker or Cullman Magnesit 528Q is a must I reckon for non-studio stuff. Incredibly useful bit of kit, I’ve no idea why all tripods aren’t made this way (I’ve got the Cullman one). Also macro focusing rails are handy but I’ve managed to amuse myself so far without.