Earthbag building requires very few tools. You mostly need sturdy, basic tools such as shovels, buckets and tampers. Buy the best quality you can afford. This may mean buying from yard sales or Craigslist to get older, higher quality tools. A lot of new stuff is junk that will fall apart in a few days or weeks.
My Earthbag Building Guide describes everything you need in detail and has lots of photos and drawings on how to make your own tampers, sliders, etc.
Note: Now I use cement buckets, not the kind in the photo.
Don’t buy anything until you think it over a long time. Chances are you don’t need it. Builders in developing countries have a bag of tools about the size of a grocery bag, and with these tools they are able to build everything up to and including large houses, apartments, shops and other structures. Now personally, I would get a few more than that, but it does show how simple building can be.