Terfpan,
Customised Rods - there are two trains of thought on thie subject.
Firstly you take an off the shelf mass production rod and then change the rings for a different pattern, reel fitting and or grip material. These changes are mainly cosmetic with maybe an enhancement in their fishing/casting ability.
Secondly there are the top of the range, hand built blanks that are made to your own requirements, weight, materials used and more importantly the action of the blank. These are usually built to your own specification, the type of rings, reel fitting and whipping thread colours. This is a true custom built rod.
The first option is relatively cheap, with the initial cost of the rod and maybe another $100 for the changes.
The second option could cost you $500 for the blank and then another $200 for the fittings. If the blank is one from the UK (Zziplex/Century/Cono-flex etc) you've then got the freight charges too.
both Anthony & Ralph are quite correct in stating that no rod will ever make up for technique or practice.
Led.