take a look at some of the all inclusive "kegging kits" at the big online retailers... they pretty much cover the basics.
typically you'll want 10' of 3/16" I.D. thick-wall beverage line per tap. you can always cut it shorter, but many get too little line and end up replacing it all to go longer.
Gas line is usually 1/4" I.D. tubing.
Barbs are usually 1/4" and work equally well for either 1/4" or 3/16" ID tubings.
I use MFL fittings on liquid lines which requires the use of barbed tailpieces and swivel nuts... the advantage is that the lines can be disassembled, swapped, used elsewhere without destroying them taking them on and off permanent barbs... as such, my Ball Lock disconnects have threaded MFL fittings instead of permanent barbs...
all hoses should be clamped down with hose clamps, either worm gear or oetiker ear/crimp types.
for the keg tap end you will need a complete shank assembly, including from back to front...
your hose clamp, shank hex or wing nut, 1/4"tailpiece, shank washer, shank body, shank flange, faucet coupling nut and faucet assembly... i would reccommend perlick faucets. again, look at the big retailer kits for "fridge conversion", they usually include all the parts to go through a fridge door or keezer collar in one kit.
you will want gasket/o-ring lube, spare o-rings for your kegs, etc.
in other words, for each beer you want to serve you will need:
MFL ball lock gas disconnect
MFL ball lock liquid disconnect
10' 3/16" ID liquid line
3-4' of 1/4"ID gas line
regulator with necessary fittings to connect 1/4"line
2 sets of 1/4" barbed swivel nuts
hose clamps for all connections
complete shank assembly with faucet
if you are running more than one keg at a time, then you may opt for dual regulators or a gas manifold to support multiple gas lines at the same pressure off one regulator.