I have done tons of battery relocation and additional battery kits...what you will need is

x amount of positive power cable (2 or 0g OFC cable should be used)
x amount of earth cable (same gauge as above), this will be used to earth the battery in the rear of the vehicle to the chassis. You can also run another length of cable from the battery to the front of the vehicle...all the connections that are usually earthed at the battery, you can connect them to a distribution block - this block can be earthed direct to chassis or ran back to the battery...this is what will dictate the earth lead length
1 or 2 distribution blocks so you can connect everything together and run the thick positive cable to the battery. Either 1 just for the positive, or add a second for the earth too
2 fuse holders - fuse the positive cable in the engine bay, and one near the battery
Crimp connectors
Battery tray or make your own

On average, most cars will use 4-5m of positive and around 1m of negative

Make sure you use PROPER OFC cable, CCA cable will just deteriorate in the engine bay when exposed to moisture/water etc

Any extra extra needed just give me a shout