It really depends on just how far into Bonsai you want to go as to what tools you will need. For just the odd tree or two, Liatris has a couple of good ideas - a bent fork as a root raker and a cheap pair of nail pincers ground to sharp edges for a basic branch cutter. My root raker is a bent phillips screwdriver and I've had that one for 20 years now. I don't have one of the expensive shop bought ones.