Some of the bonsai tool sets look tempting but I've just bought tools over the years as I needed them, initially proper small leaf/stem scissors, the 'shear' type sold as herb cutters are good too for leaf trimming and very cheap, a concave branch cutter and bonsai wire cutter are other essentials. I found it's worth keeping a really sharp garden pruner just for bonsai use along with assorted small brushes, and of course a small tool bag to keep everything together (plus an oily rag for cleaning). Mostly bought online (Amazon or Ebay) and I have just ordered 180mm long handled scissors from Amazon for about £7 which will pretty well complete my toolkit, for now...
Dave