I have virtually no tools but it'd definitely help to have the right ones when I need them.
So there are some good infos here to read up:
http://www.automotiveforums.com/t956697-basic_auto_mechanic_tools.html
"For a beginner, doing basic work, I will cheat and suggest an entire
tool kit or kits. Some decent retailers will sell a 200-300 piece tool
set for a very decent price.
Typically these sets include a full set of standard and metric sockets
(in both deep and shallow), from 4mm (or very small) all the way to 24
mm. In standard, 1/4 inch all the way to 1 1/4 is good. Also, 1/4, 3/8
1nd 1/2 inch drives are required, with corresponding short, medium and
long extensions and swivel joints for each drive size. Allen and Torx
sockets for the larger sizes are handy.
Add a set of quality slot, phillips (3 sizes for each) and Torx
screwdrivers and a set of both metric and standard Allen wrenches.
Additionally, both big and small examples of vice grips, slip-joint
pliers, linesman's pliers, waterpump (Channel-Lock) pliers, side
cutters, ball-peen hammers, wire brushes, pry bars, cold chisels, pin
punches, flat punches, mill files, and adjustable (Crescent) wrenches.
A full set of standard and metric combination wrenches is good to have;
Other items include marker pens, tie wraps (various sizes) electrical
tape, masking tape, wire stripper/crimper, C-clamps, sharp knife,
worklight, floor jack and jackstands, strap and cup-style oil filter
wrenches, grease gun, test light, multimeter, feeler gauge, tire
pressure gauge, timing light, jumper cable, siphon hose, assorted
funnels, drain pan
Imho all these tools are essential, even if you do not think you need
them right away. Assembling a kit like this is not particularly
expensive, either. There are many decent quality, affordable tools out
there, far more than there was 20-25 years ago.
Cheap (often China or India sourced) tools have flooded the market. Some
are okay, especially for light-duty work. Some simply are fakes.
I would stick to tools sold by major chain retailers, especially ones
with a lifetime replacement warranty. I have found that Sears sells
affordable yet excellent tools.
I have bought some very good tools with odd, unknown brand names, at
auto swap meets. I have also bought absolute crap from similar sources,
so just be careful."
http://www.automedia.com/10_Best_Car_Care_Tools/ccr20110101ct/1