When you say you don't want the thick stuff, I assume you want 3/8th or 1/4 inch inner diameter tubing?
Basically all the major components you want have standard G1/4 fittings so you just buy all the oft recommended parts and screw in the fittings you want - 1/2", 3/8" or 1/4".
I doubt you'll see a great system with 1/4" tubing. I run 3/8ths as I have lot of close-together components and 1/2" doesn't bend tight enough. I use XSPC Springz to keep it all smoothly curved, with no kinks.
I think you could do worse than start off with an XSPC kit, which is 3/8ths throughout and, although it's not fantastic, it's better than an air cooler and it's quite cheap for water cooling at about £70 for the block, radiator, pump/reservoir and tubing.
I put one into a friends system because they wanted it to glow in the dark (Blue Feser 1 UV Fluid) and it works really well, they have an E4300 overclocked to 2.7GHz and it runs at 28C idle and 49C maxed out with TAT.