Hi Oboebunny
A good reed knife is essential, as is the stone to keep it sharp. Whilst you may not need the most lavish of knives, a good quality is essential if you are going to manage to work well with your cane and not wreck it as you go. Keeping it sharp is also an essential, so the stone is very important (and the oil to put on it).
After that you should have a mandrel (the bit that goes inside the staple to help you hold it and keep it in shape whilst you work) and a plaque to put between the blades of the reed. If you are tying your own reeds you'd benefit from having a cutting block (for preparing the tip) but it's not absolutely essential.
Strictly speaking, apart from thread to tie on with, nail-varnish to seal the binding, some wire and pliers if you like wired reeds and some "cling-film" (the cheaper option than goldbeaters' skin for sealing the reed) you don't have to own anything else, provided you plan to buy gouged and shaped cane (ie ready to tie on) or you propose to buy part-scraped reeds (quite a good way to start initially).
If you get the bug for doing this sort of thing, eventually a shaper and, maybe a gouging machine will be something you'll want but, in the early days, you don't need them.
One tip: keep any old reeds that no longer play to practise your scraping technique. You're unlikely to master the technique straight off and so working on essentially "dead" reeds is a great way to master use of the knife and getting the balance right in your knife hand.
Making your own reeds is certainly much cheaper

but it's a frustrating art much of the time.

Lots of effort and then in a micro-second the wretched thing breaks and you start all over again. Worth doing things in batches (ie tie on several at a time, part-scrape a group and so on) and allow plenty of time and soaking of cane for your efforts. The more you try to rush, the more likely a failure.
Best of luck!