I echo aaxxonns reply re. the 2 tools(pruners, and concave cutters), start there and expand as you and your trees grow, next would probably be wire cutters, the one meant for bonsai are much better than anything you will find for cutting wire off your trees, then grow your set as needed.
If available get them from a nearby Bonsai nursery, if not go online to a bonsai retailer.
I tend to get better tools( best that I can afford), they have more value in the long run.